UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 20-F

(Mark One)

OR

For the fiscal year ended December 31, 2013.2014.

OR

OR

Date of event requiring this shell company report

For the transition period fromto

Commission file number: 001-35126

21Vianet Group, Inc.

(Exact Name of Registrant as Specified in Its Charter)

N/A

(Translation of Registrant’s Name into English)

Cayman Islands

(Jurisdiction of Incorporation or Organization)

M5, 1 Jiuxianqiao East Road,

Chaoyang District

Beijing, 100016

The People’s Republic of China

(Address of Principal Executive Offices)

Mr. Shang-Wen Hsiao, Chief Financial Officer

21Vianet Group, Inc.

M5, 1 Jiuxianqiao East Road,

Chaoyang District

Beijing, 100016

The People’s Republic of China

Phone: (86) 10 8456-2121

Facsimile: (86) 10 8456-2619

(Name, Telephone, E-mail and/or Facsimile Number and Address of Company Contact Person)

Securities registered or to be registered pursuant to Section 12(b) of the Act:

Securities registered or to be registered pursuant to Section 12(g) of the Act:

None

(Title of Class)

Securities for which there is a reporting obligation pursuant to Section 15(d) of the Act:

None

(Title of Class)

Indicate the number of outstanding shares of each of the Issuer’s classes of capital or common stock as of the close of the period covered by the annual report: 344,745,991346,803,765 Class A ordinary shares and 53,480,54449,430,544 Class B ordinary shares, par value US$0.00001 per share, as of December 31, 2013.2014.

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  þ    No  ¨

If this report is an annual or transition report, indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.    Yes  ¨    No  þ

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  þ    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or such shorter period that the registrant was required to submit and post such files).    Yes  þ    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer  ¨þ                Accelerated filer  þ¨                Non-accelerated filer  ¨

Indicate by check mark which basis of accounting the registrant has used to prepare the financial statements included in this filing:

If “Other” has been checked in response to the previous question, indicate by check mark which financial statement item the registrant has elected to follow.

Item 17  ¨             Item 18  ¨

If this is an annual report, indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  þ

(APPLICABLE ONLY TO ISSUERS INVOLVED IN BANKRUPTCY PROCEEDINGS DURING THE PAST FIVE YEARS)

Indicate by check mark whether the registrant has filed all documents and reports required to be filed by Sections 12, 13 or 15(d) of the Securities Exchange Act of 1934 subsequent to the distribution of securities under a plan confirmed by a court.    Yes  ¨    No  ¨

TABLE OF CONTENTS

i

INTRODUCTION

Unless otherwise indicated and except where the context otherwise requires, references in this annual report on Form 20-F to:

FORWARD-LOOKING STATEMENTS

This annual report on Form 20-F contains forward-looking statements that involve risks and uncertainties. All statements other than statements of historical facts are forward-looking statements. These forward-looking statements are made under the “safe harbor” provisions of the U.S. Private Securities Litigation Reform Act of 1995. Known and unknown risks, uncertainties and other factors, including those listed under “Risk Factors,” may cause our actual results, performance or achievements to be materially different from those expressed or implied by the forward-looking statements.

You can identify some of these forward-looking statements by words or phrases such as “may,” “will,” “expect,” “anticipate,” “aim,” “estimate,” “intend,” “plan,” “believe,” “is/are likely to,” “potential,” “continue” or other similar expressions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy and financial needs. These forward-looking statements include:

These forward-looking statements involve various risks and uncertainties. Although we believe that our expectations expressed in these forward-looking statements are reasonable, our expectations may later be found to be incorrect. Our actual results could be materially different from our expectations. Other sections of this annual report include additional factors that could adversely impact our business and financial performance. Moreover, we operate in an evolving environment. New risk factors and uncertainties emerge from time to time and it is not possible for our management to predict all risk factors and uncertainties, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements. You should read thoroughly this annual report and the documents that we refer to with the understanding that our actual future results may be materially different from and worse than what we expect. We qualify all of our forward-looking statements by these cautionary statements.

PART I

Not applicable.

Not applicable.

A.Selected Financial Data

Selected Consolidated Financial Data

The following selected consolidated financial information for the periods and as of the dates indicated should be read in conjunction with our consolidated financial statements and related notes and “Item 5. Operating and Financial Review and Prospects” in this annual report.

Our selected consolidated financial data presented below for the years ended December 31, 2011, 2012, 2013 and 20132014 and our balance sheet data as of December 31, 20122013 and 20132014 have been derived from our audited consolidated financial statements included elsewhere in this annual report. Our audited consolidated financial statements are prepared in accordance with U.S. GAAP.

Our selected consolidated financial data presented below for the year ended December 31, 20092010 and 20102011 and our balance sheet data as of December 31, 2009, 2010, 2011 and 20112012 have been derived from our audited financial statements not included in this annual report.

The following table presents a summary of our consolidated balance sheet data as of December 31, 2009, 2010, 2011, 2012, 2013 and 2013.2014.

Discussion of Non-GAAP Financial Measures

In evaluating our business, we consider and use the following non-GAAP measures as supplemental measures to review and assess our operating performance: adjusted gross profit, adjusted operating expenses, adjusted net profit and adjusted EBITDA. The presentation of these non-GAAP financial measures is not intended to be considered in isolation or as a substitute for the financial information prepared and presented in accordance with U.S. GAAP. We define adjusted gross profit as gross profit excluding share-based compensation expenses and amortization expenses of intangible assets derived from acquisitions. We define adjusted operating expenses as operating expenses excluding share-based compensation expenses and changes in the fair value of contingent purchase consideration payable. We define adjusted net profit as net (loss) profit from continuing operations excluding share-based compensation expenses, amortization expenses of intangible assets derived from acquisitions, changes in the fair value of contingent purchase consideration payable and unrecognized tax benefits, tax incentive receipt and outside basis difference.loss on debt extinguishment. We define adjusted EBITDA as EBITDA excluding share-based compensation expenses, and changes in the fair value of contingent purchase consideration payable and loss on debt extinguishment, and EBITDA as net profit (loss) from continuing operations before income tax expense (benefit), foreign exchange gain (loss), other expenses, other income, interest expense, interest income and depreciation and amortization.

The non-GAAP financial measure disclosed by us should not be considered a substitute for financial measures prepared in accordance with U.S. GAAP. You should carefully evaluate the financial results we have

reported in accordance with U.S. GAAP and our reconciliation of GAAP to non-GAAP results. The non-GAAP financial measure used by us may be prepared differently from and, therefore, may not be comparable to similarly titled measures used by other companies.

We believe that the use of these non-GAAP measures facilitates investors’ assessment of our operating performance from period to period and from company to company by backing out potential differences caused by variations in items such as capital structures (affecting relative interest expenses), the book amortization of intangibles (affecting relative amortization expenses), the age and book value of property and equipment (affecting relative depreciation expenses) and other non-cash expenses (affecting share-based compensation expenses). We also present these non-GAAP measures because we believe these non-GAAP measures are frequently used by securities analysts, investors and other interested parties as measures of the financial performance of companies in our industry.

These non-GAAP financial measures are not defined under U.S. GAAP and are not measures presented in accordance with U.S. GAAP. These non-GAAP financial measures have limitations as analytical tools, and when assessing our operating performance, investors should not consider them in isolation, or as a substitute for net income (loss) or other consolidated income statement data prepared in accordance with U.S. GAAP. Some of these limitations include, but are not limited to:

We compensate for these limitations by relying primarily on our U.S. GAAP results and using adjusted gross profit, adjusted operating expenses, adjusted net profit and adjusted EBITDA only as supplemental measures. Our adjusted gross profit, adjusted operating expenses, adjusted net profit and adjusted EBITDA are calculated as follows for the periods presented:

Exchange Rate Information

AllSubstantially all of our operations are conducted in China and substantially all of our revenues are denominated in Renminbi. This annual report contains translations of Renminbi amounts into U.S. dollars at specific rates solely for the convenience of the reader. For all dates and periods through December 31, 2008, theThe conversion of RMB into U.S. dollars in this annual report is based on the noon buying rate in New York City for cable transfers of RMB as certified for customs purposes by the Federal Reserve Bank of New York. For January 1, 2009 and all later dates and periods, the exchange rate refers to the exchange rate as set forth in the H.10 statistical release of the Federal Reserve Board. Unless otherwise noted, all translations from RMB to U.S. dollars and from U.S. dollars to RMB in this annual report were made at a rate of RMB6.0537RMB6.2046 to US$1.00, the noon buying rate in effect as of December 31, 2013.2014. We make no representation that any RMB or U.S. dollar amounts could have been, or could be, converted into U.S. dollars or RMB, as the case may be, at any particular rate, or at all. The PRC government imposes control over its foreign currency reserves in part through direct regulation of the conversion of RMB into foreign exchange and through restrictions on foreign trade. On April 4, 2014,3, 2015, the noon buying rate was RMB6.2118RMB6.1930 to US$1.00.

The following table sets forth information concerning exchange rates between the RMB and the U.S. dollar for the periods indicated.

Source: Federal Reserve Statistical Release

B.Capitalization and Indebtedness

Not applicable.

C.Reasons for the Offer and Use of Proceeds

Not applicable.

D.Risk Factors

Risks Related to Our Business and Industry

We may not be able to successfully implement our growth strategies.

We plan to further increase our services capacities. We plan to increaseIn 2014, we increased the aggregate number of cabinets under our management from 14,041by more than 7,400 to approximately 21,500. In order to support our growing customer demand, we plan to add a similar level of new cabinets asin 2015 through new self-built data centers, new phases of December 31, 2013 to 25,000 cabinets by the end of 2014 through adding newexisting self-built data centers and partnered data centers. In addition, we plan to expand our private optical fiber network to cover all of our major data centers throughout China and plan to increase our network services capacity. To achieve this expansion plan, we will be required to commit a substantial amount of operating and financial resources. Our planned capital expenditures, together with our ongoing operating expenses, will cause substantial cash outflows. If we are not able to generate sufficient operating cash flows or obtain other types ofalternative financings, our ability to fund our growth strategy may be limited. AdditionalAlternative debt or equity financing may not be available when needed or, if available, may not be available on satisfactory terms. Any inability to obtain additional debt or equity financing or to generate sufficient cash from operations may require us to prioritize projects or curtail capital expenditures and could adversely affect our results of operations.

In addition, site selection is a critical factor in our expansion plans, and there may not be suitable properties available with the necessary combination of high power capacity and optical fiber connectivity, which may have

a negative impact on our revenue growth. Moreover, we may not have sufficient customer demand in the markets where our data centers are located. We may overestimate the demand for our services and as a result may increase our data center capacity or expand our internet network more aggressively than needed, resulting in a negative impact to our gross profit margins. Furthermore, the costs of construction and maintenance of new data centers constitute a significant portion of our capital expenditures and operating expenses. If our planned expansion does not achieve the desired results, our operating margins could be materially reduced, which would materially impair our profitability and adversely affect our business and results of operations.

Delays in the construction of new data centers or the expansion of existing data centers could involve significant risks to our business.

In order to meet customer demand in some of our existing and new markets, we need to expand existing data centers, lease new facilities or obtain suitable land to build new data centers. Expansion of existing data centers and/or construction of new data centers are currently underway, or being contemplated, in many of our markets. Such expansion and/or construction require us to carefully select and rely on the experience of one or more designers, general contractors, and subcontractors during the design and construction process. If a designer, general contractor, or significant subcontractor experiences financial or other problems during the design or construction process, we could experience significant delays and/or incur increased costs to complete the projects, resulting in negative impacts on our results of operations.

In addition, we need to work closely with the local power suppliers where our proposed data centers are located. If we experience significant delays in the supply of power required to support the data center expansion or new construction, either during the design or construction phases, the progress of the data center expansion and/or construction could deviate from our original plans, which could cause material and negative effect to our revenue growth, profitability and results of operations.

Any significant or prolonged failure in our infrastructure or services would lead to significant costs and disruptions and would reduce our revenues, harm our business reputation and have a material adverse effect on our financial results.

Our data centers, power supplies and network are vulnerable to disruptions and to failure. Problems with the cooling equipment, generators, backup batteries, routers, switches, or other equipment, whether or not within our control, could result in service interruptions and data losses for our customers as well as equipment damage. Our customers locate their computing and networking equipment in our data centers, and any significant or prolonged failure in our infrastructure or services could significantly disrupt the normal business operations of our customers and harm our reputation and reduce our revenue. While we offer data backup services and disaster recovery services, which could mitigate the adverse effects of such a failure, most of our customers do not subscribe for these services. Accordingly, any failure or downtime in one of our data centers could affect many of our customers. The total destruction or severe impairment of any of our data centers could result in significant downtime of our services and loss of customer data. Since our ability to attract and retain customers depends on our ability to provide highly reliable service, even minor interruptions in our service could harm our reputation.

While we have not experienced any material interruptions in the past, services interruptions continue to be a significant risk for us and could materially impact our business. Any services interruptions could:

Any of these events could materially increase our expenses or reduce our revenue, which would have a material adverse effect on our results of operations.

We compete with, and our business substantially depends on, China Telecom and China Unicom for hosting facilities and other telecommunication resources.

Our business depends on our relationships with China Telecom and China Unicom, two major telecommunications carriers in China, for hosting facilities and bandwidth, and to some extent, for optical fibers. We directly enter into agreements with the local subsidiaries of China Telecom or China Unicom, from which we lease cabinets in the data centers built and operated by them, with power systems, cabling and wiring and other data center equipment pre-installed. Because each local subsidiary of China Telecom or China Unicom has independent authority and budget to enter into contracts, our contract terms with these subsidiaries vary and are determined on a case-by-case basis. We generally refer to this type ofdefine “partnered” data centers as the data center space and cabinets we leased from China Telecom, China Unicom and other third parties through agreements. Based on the specific requests of our “partnered”customers, demands in different cities and our strategy for points of presence, or POP, establishment, the locations and number of our partnered data centers.centers may change from time to time. As of December 31, 2013,2014, we leased a total of 3,6516,950 cabinets from local subsidiaries of China Telecom and China Unicom that are housed in our 6373 partnered data centers, accounting for 26%32.3% of the total number of our cabinets under management. If we are not able to secure sufficient cabinets from China Unicom and China

Telecom, it will have a material adverse effect on our business prospects and results of operations. We also rely on China Telecom and China Unicom for a significant portion of our bandwidth needs and lease optical fibers from them to connect our data centers with each other and with the telecommunications backbones and other internet service providers, or ISPs. Our agreements with local subsidiaries of China Telecom or China Unicom usually have a one-year term with automatic renewal option. In addition, China Telecom and China Unicom also provide data center services and directly compete with us for customers. See “—We may not be able to compete effectively against our current and future competitors.” We believe that we have good business relationships with China Telecom and China Unicom, and we have access to adequate hosting facilities, bandwidth and optical fibers to provide our services. However, there can be no assurance that we can always secure hosting facilities and bandwidth from China Telecom and China Unicom on commercially acceptable terms, or at all. As a result, our business and results of operations would be materially and adversely affected.

Our leases for data centers could be terminated early, we may not be able to renew our existing leases on commercially reasonable terms, and our rent could increase substantially in the future, which could materially and adversely affect our operations.

We lease buildings with suitable power supplies and safe structures meeting our data center requirements and convert them into data centers by installing power generators, air conditioning systems, cables, cabinets and other equipment. We also build our own data centers after obtaining suitable land. We generally refer to this typethese two types of data centers as “self-built” data centers. Our operating leases generally have three to ten yeartwenty years lease terms with renewal options. As of December 31, 2013,2014, our self-built data centers house 9,13114,572 cabinets, or 65%67.7% of the total number of our cabinets under our management. We plan to renew our existing leases upon expiration. However, we may not be able to renew these leases on commercially reasonable terms, if at all. We may experience an increase in our rent payments. In addition, although the lessors of our self-built data centers generally do not have the right of early termination and we have not experienced any early termination as of the date of this annual report, the lease could be terminated early if we are in material breach of the lease agreements or the leased premises become unavailable due to reasons beyond the lessors’ control. If any such event happens,our leases for data centers were terminated early, we may have to relocate our data center equipment and the servers and equipment of our customers to a new building and incur significant cost related to relocation. Any relocation could also affect our ability to provide services and harm our reputation. As a result, our business and results of operations could be materially and adversely affected.

We have been named as a defendant in two putative shareholder class action lawsuits that could have a material adverse impact on our business, financial condition, results of operation, cash flows and reputation.

We will have to defend against the putative shareholder class action lawsuits described in “Item 8. Financial Information—A. Consolidated Statements and Other Financial Information—Legal and Administrative Proceedings—Litigation,” including any appeals of such lawsuits should our initial defense be unsuccessful. We are currently unable to estimate the possible loss or possible range of loss, if any, associated with the resolution of these lawsuits. In the event that our initial defense of these lawsuits is unsuccessful, there can be no assurance that we will prevail in any appeal. Any adverse outcome of these cases, including any plaintiff’s appeal of a judgment in these lawsuits, could have a material adverse effect on our business, financial condition, results of operation, cash flows and reputation. In addition, there can be no assurance that our insurance carriers will cover all or part of the defense costs, or any liabilities that may arise from these matters. The litigation process may utilize a significant portion of our cash resources and divert management’s attention from the day-to-day operations of our company, all of which could harm our business. We also may be subject to claims for indemnification related to these matters, and we cannot predict the impact that indemnification claims may have on our business or financial results.

Investment in broadband wireless access services in Hong Kong may have a material adverse effect on our business prospects and results of operations.

In February 2012, we won a bid for radio spectrum in the 2.3 GHz band to provide broadband wireless access services in Hong Kong for HK$150 million. This investment provides us an opportunity to enter into the mobile infrastructure landscape and explore the market potentials in providing wireless solutions. We planhave been in negotiations with some Hong Kong local carriers to form a partnership or a joint venture with Hong Kong local carriers and aim to use the broadband wireless access license as an investment or a form of contribution in the partnership or joint venture to take advantage of the local knowledge and market intelligence of service providers in Hong Kong. Currently, we do not plan to incur significant capital expenditure to build the infrastructures in Hong Kong by ourselves. However, we have limited experience in providing mobile infrastructure services in Hong Kong. We may not be able to successfully find anegotiate with certain Hong Kong local carriercarrier(s) to work with us, and the performance bond in the amount of HK$150 million submitted by us to the Hong Kong Telecommunications Authority may be withheld if we fail to successfully fulfill the requirements for the broadband wireless access license by ourselves, and furthermore, our investment in the broadband wireless access license may divert our management’s attention from our core business in mainland China, which maywould have a material adverse effect on our business prospects and results of operations.

Difficulties in identifying, consummating and integrating acquisitions and alliances and potential write-off in connection with our investment or acquisitions may have a material and adverse effect on our business and results of operations.

As part of our growth strategy, we have acquired, and may in the future acquire, companies that are complementary to our business. From time to time, we may also make alternative investments and enter into strategic partnerships or alliances as we see fit. For example, in October 2012, we entered into a commercial operator agreement with Microsoft Corporation to expand Microsoft’s premier commercial public cloud services, Office 365 and Windows Azure, in China.China, the term of which was extended to December 31, 2018. In February 2013, we acquired 100% equity interests in Beijing

Tianwang Online Communication Technology Co., Ltd., or BeijingBJ Tianwang, and Beijing Yilong Xinda Technology Co., Ltd., or Beijing Yilong Xinda.BJ Yilong. These two companies principally provide virtual private network services and managed network services. In April 2013, we completed the acquisition of 100% equity interests in iJoy Holding Limited, or iJoy BVI, and its subsidiaries (collectively known as “iJoy”) with a purchase consideration of RMB97.0 million. In June 2013, we entered into a strategic agreement with Dongguan Dongcai Investment Holdings Limited, or Dongguan Dongcai, and established Dongguan Asia Cloud Investment Co., Ltd., or Asia Cloud Investment, to build a new internet data center, provide cloud computing related services in Dongguan as well as create a research and development team that will focus on developing and implementing next generation networking technologies. In December 2013, we

entered into a definitive agreement with IBM to introduce IBM’s premier private cloud infrastructure service and bring high-value managed private and hybrid cloud services to China. IBM will provide the physical point of distribution, or POD, and service while we will host the POD facility at our data centers in Beijing. In May 2014, we acquired 50% equity interests plus one share in Sichuan Aipu Network Co., Ltd. and its affiliates (collectively, the “Aipu Group”). Aipu Group principally provides last-mile wired broadband access and other value-added services. In August 2014, we acquired 100% equity interests in Dermot Holdings Limited and its subsidiaries (collectively, the “Dermot Entities”) to expand our data transmission infrastructure across the Greater China region and deliver high-performance virtual private network (VPN) connectivity solutions by utilizing Dermot Entities’ advanced network and infrastructure. However, past and future acquisitions, partnerships or alliances may expose us to potential risks, including risks associated with:

Any of the potential risks listed above could have a material and adverse effect on our ability to manage our business and our results of operation.

In addition, we record goodwill if the purchase price we pay in the acquisitions exceeded the amount assigned to the fair value of the net assets or business acquired. We are required to test our goodwill and intangible assets for impairment annually or more frequently if events or changes in circumstances indicate that they may be impaired. We may record impairment of goodwill and acquired intangible assets in connection with our acquisitions if the carrying value of our acquisition goodwill and related acquired intangible assets in connection with our past or future acquisitions are determined to be impaired. We cannot be assured the acquired businesses, technologies, services and products from our past acquisitions and any potential transaction will generate sufficient revenue to offset the associated costs or other potential unforeseen adverse effects on our business. Furthermore, we may need to raise additional debt or sell additional equity or equity-linked securities to make or complete such acquisitions. See “—We may require additional capital to meet our future capital needs, which may adversely affect our financial position and result in additional shareholder dilution.”

We may not be able to increase sales to our existing customers and add new customers, which would adversely affect our results of operations.

Our growth depends on our ability to continue to expand our service offerings to existing customers and attract new customers. We may be unable to sustain our growth for a number of reasons, such as:

A substantial amount of our past revenues were derived from service upgrades by existing customers. Our costs associated with increasing revenues from existing customers are generally lower than costs associated with generating revenues from new customers. Therefore, slowing revenue growth or declining revenues from our existing customers, even if offset by an increase in revenues from new customers, could reduce our operating margins. Any failure to continue attracting new customers or grow our revenues from existing customers for a prolonged period of time could have a material adverse effect on our results of operations.

We may not be able to compete effectively against our current and future competitors.

We face competition from various industry players, including carriers such as China Telecom and China Unicom, carrier-neutral service providers in China such as ChinaNetCenter and Dr. Peng, content delivery network (CDN) service provider such as ChinaCache and the in-house data centers of major corporations, cloud services providers such as AliCloud, as well as new market entrants in the future. As we enter into the cloud serviceslast-mile wired broadband market and VPN market, we may face more competition from variousmore market players. Competition is primarily centered on the quality of service and technical expertise, security, reliability and functionality, reputation and brand recognition, financial strength, the breadth and depth of services offered, and price. Some of our current and future competitors have substantially greater financial, technical and marketing resources, greater brand recognition, and more established relationships in the industry than we do. As a result, some of these competitors may be able to:

If we are unable to compete effectively and successfully against our current and future competitors, our business prospects, financial condition and results of operations could be materially and adversely affected.

We depend on third-party suppliers for key elements of our network infrastructure, and our financial performance and results of operation could suffer if we fail to manage supplier issue properly.

To provide connectivity services to our customers, we purchase network connections from several network service providers, primarily China Telecom and China Unicom. We can offer no assurances that these service providers will continue to provide service to us on a cost-effective basis or on otherwise competitive terms, if at all, or that these providers will provide us with additional capacity to adequately meet customer demand or to expand our business. Any of these factors could limit our growth prospects and materially and adversely affect our business.

We also depend on third parties for optical fibers for our data transmission network. We offer no assurance that we will be able to maintain a good relationship with our optical fiber providers or renew our leases on commercially reasonably terms, if at all. The occurrence of these events would materially and adversely affect our ability to provide services and affect our business and results of operations.

In addition, we currently purchase routers, switches and other equipment from a limited number of suppliers. We do not carry significant inventories of the products we purchase, and we have no guaranteed supply arrangements with our suppliers. The loss of a significant vendor could delay any build-out of our infrastructure and increase our costs. If our suppliers fail to provide products or services that comply with evolving internet standards or that interoperate with other products or services we use in our network infrastructure, we may be unable to meet all or a portion of our customer service commitments, which could materially and adversely affect our results of operations.

Our self-built and partnered data centers are vulnerable to security breaches, which could disrupt our operations and have a material adverse effect on our business, financial performance and results of operations.

A party who is able to compromise the security measures of our data centers and networks or the security of our infrastructure could misappropriate either our proprietary information or the information of our customers, or cause interruptions or malfunctions in our operations. In addition, we have limited control over our partnered data centers, which are primarily operated by China Telecom or China Unicom. We may be required to devote significant capital and resources to protect against such threats or to alleviate problems caused by security breaches. As techniques used to breach security change frequently and are generally not recognized until launched against a target, we may not be able to implement security measures in a timely manner or, if and when implemented, we may not be certain whether these measures could be circumvented. Any breaches that may occur could expose us to increased risk of lawsuits, regulatory penalties, loss of existing or potential customers, harm to our reputation and significant increases in our security costs, which could have a material adverse effect on our financial performance and results of operations.

We depend on third parties for telecommunication network services, and increased telecommunications costs may adversely affect our results of operations.

Our success depends in part upon the capacity, reliability, and performance of our network infrastructure, including the capacity leased from our internet bandwidth suppliers, which are primarily China Telecom and China Unicom. We depend on these companies to provide us with uninterrupted and error-free services through their telecommunications networks. However, some of these providers are also our competitors and we exercise little control over our bandwidth suppliers. In addition, we have experienced and expect to continue to experience interruptions or delays in network services. Any failure on our part or the part of our third-party suppliers to achieve or maintain high data transmission capacity, reliability or performance could significantly reduce customer demand for our services and damage our business and reputation.

As our customer base grows and their usage of telecommunications capacityresources increases, we may be required to make additional investments in our capacity to maintain adequate data transmission speed. The availability of such capacity may be limited or the cost may be unacceptable to us. If adequate capacity is not available to us as our customers’ usage increases, our network may be unable to achieve or maintain sufficiently high data transmission capacity, reliability or performance. In addition, our operating margins may suffer if our bandwidth suppliers increase the prices for their services and we are unable to pass along the increased costs to our customers.

A severe or prolonged downturn in the global or Chinese economy could materially and adversely affect our business and our results of operation.

The global economymacroeconomic environment is still recovering fromfacing challenges, including the recent financial crisis. Continued concerns aboutescalation of the systemic impactEuropean sovereign debt crisis since 2011, the end of potential long-term and wide-spread recession, energy costs, geopolitical issues,quantitative easing by the U.S. Federal Reserve and the availability and cost of credit have contributed to increased market volatility and diminished expectations for economic growth around

slowdown in the world. The difficult economic outlook has negatively affected business and consumer confidence and contributed to high volatility. While the Chinese economy has recovered more quickly than some other major economies, it still faces challenges. The long-term effects of the stimulus plans and other measures implemented by the Chinese government since 2008 remain to be seen.

Eurozone in 2014. Our business and operations are primarily based in China and substantially all of our revenues are derived from our operations in China. Accordingly, our financial results have been, and are expected to continue to be, affected by the economy and data center services industry in China. Although the economy in China has grown significantly in the past decades, it still faces challenges. The long-term effectsChinese economy has slowed down in recent years. According to the National Bureau of Statistics of China, China’s gross domestic product (GDP) growth slowed to 7.4% in 2014. There have been concerns over unrest in the stimulus plansMiddle East and Africa, which have resulted in volatility in oil and other measures implemented bymarkets, and over the Chinese government since 2008 remainpossibility of a war involving Ukraine. There have also been concerns on the relationship among China and other Asian countries, which may result in or intensify potential conflicts in relation to be seen. China’s GDP grew by 7.7% from 2012territorial disputes. Economic conditions in China are sensitive to 2013,global economic conditions, as well as changes in domestic economic and political policies and the slowest since 1999.expected or perceived overall economic growth rate in China. Any severe or prolonged slowdown in the global and/or Chinese economy may have a negative impact on our business, results of operations and financial condition, and continued turbulence in the international markets may adversely affect our ability to access the capital markets to meet liquidity needs.

If we are unable to meet our customers’ requirements, our reputation and results of operations could suffer.

Our agreements with our customers contain certain guarantees regarding our performance. For hosting services, we guarantee 99.99% uptime for power and 99.9% uptime for network connectivity, failure of which will cause us to provide free service for the following month. Although we have not had any material customer claims for power failures or network disruptions, our success depends on our ability to meet or exceed our customers’ expectations. We have not had any major customer service issues in the past. However, if in the future we are unable to provide customers with quality customer support, we could face customer dissatisfaction, decreased overall demand for our services, and loss of revenue. In addition, inability to meet customer service expectations may damage our reputation and could consequently limit our ability to retain existing customers and attract new customers, which would adversely affect our ability to generate revenue and negatively impact our results of operations.

We rely on customers in the internet industry for most of our revenues.

We derived over a majority of our revenues in 20132014 from customers in China’s internet industry, including online media, e-commerce, online game companies, portals, search engines, mobile internet and mobile internet.cloud services providers. The business models of some internet companies are relatively new and have not been well proven. Many internet companies base their business prospects on the continued growth of China’s internet market, which may not happen as expected.

In addition, our business would suffer if companies in China’s internet sector reduce the outsourcing of their data center services. If any of these events happen, we may lose customers or have difficulties in selling our services, which would materially and adversely affect our business and results of operations.

We may require additional capital to meet our future capital needs, which may adversely affect our financial position and result in additional shareholder dilution.

We will require significant capital expenditures to fund our future growth. We may need to raise additional funds through equity or debt financings in the future in order to meet our capital needs in relation to the construction of our self-built data centers.

In March 2013, we issued RMB1 billion (US$165.2 million) in aggregate principal amount of RMB denominated bonds due 2016 with a coupon rate of 7.875% per annum, or the 2016 Bonds. Interest on the 2016 Bonds is payable semi-annually in arrears on, or nearest to, March 22 and September 22 in each year, beginning on September 22, 2013. TheIn June 2014, we issued RMB2 billion (US$322.3 million) in aggregate principal amount of RMB denominated bonds due 2017 at an interest rate of 6.875% per annum, or the 2017 Bonds, and used a portion of the proceeds to

purchase, pursuant to a tender offer, substantially all the 2016 Bonds, with only RMB264.3 million (US$42.6 million) of the principal amount of the 2016 Bonds outstanding as of December 31, 2014. Interest on the 2017 Bonds is payable semi-annually in arrears on, or nearest to, June 26 and December 26 in each year, beginning on December 26, 2014. Both of the 2016 Bonds and 2017 Bonds have restrictive covenants relating to financial ratios as well as our capital raising activities and other financial and operational matters, which may make it more difficult for us to obtain additional capital and to pursue business opportunities, including potential acquisitions. Such covenants restrict our abilities to declare dividends or incur or guarantee additional indebtedness, among other things. On September 30,See “Item 5. Operating and Financial Review and Prospects—B. Liquidity and Capital Resources” for more detailed information on restrictive covenants of the 2016 Bonds and 2017 Bonds.

In October 2013, Esta Investments Pte Ltd, or Esta, entered into a purchase agreement with us to subscribe forwe issued 34,683,042 of our newly issued Class A ordinary shares (in the form of 5,780,507 ADSs) at the priceto Esta Investments Pte Ltd, or Esta, for an aggregate cash consideration of US$2.5 per Class A ordinary share and acquire86.7 million. In addition, Esta purchased 5,316,960 Class A ordinary shares (in the form of 886,160 ADSs) from certain of our existing shareholders atfor a total cash consideration of US$13.3 million which was paid to the priceselling shareholders through us.

In January 2015, we issued (i) 39,087,125 Class A and 18,250,268 Class B ordinary shares to King Venture Holdings Limited, or Kingsoft, for an aggregate cash consideration of US$2.5 per172 million; (ii) 6,142,410 Class A and 10,524,257 Class B ordinary shares to Xiaomi Ventures Limited, or Xiaomi, for an aggregate cash consideration of US$50 million; and (iii) 24,668,020 Class A ordinary share. shares (in the form of 4,111,337 ADSs) to Esta, for an aggregate cash consideration of US$74 million.

If we raise additional funds through further issuances of equity or equity-linked securities, our existing shareholders could suffer significant dilution in their percentage ownership of our company, and any new equity securities we issue could have rights, preferences, and privileges senior to those of holders of our ADSs or ordinary shares.

Servicing our debt requires a significant amount of cash, and we may not have sufficient cash flow from our business to pay our debt.

Our ability to make scheduled payments of the principal of, to pay interest on or to refinance our indebtedness, including the 2016 Bonds and 2017 Bonds, depends on our future performance, which is subject to economic, financial, competitive and other factors beyond our control. Our business may not continue to generate cash flow from operations in the future sufficient to service our debt and make necessary capital expenditures. If we are unable to generate such cash flow, we may be required to adopt one or more alternatives, such as selling assets, restructuring debt or obtaining additional equity capital on terms that may be onerous or highly dilutive. Our ability to refinance our indebtedness will depend on the capital markets and our financial condition at such time. We may not be able to engage in any of these activities or engage in these activities on desirable terms, which could result in a default on our debt obligations.

As of December 31, 2013,2014, our total consolidated indebtedness and other liabilities representing total bank and other borrowings, bonds payables, accounts payable, notes payable and accrued expenses and other payables were RMB2,915.6RMB4,527.1 million (US$481.6729.6 million). Failure to servicing our debt would constitute an event of default under the terms of the bonds, which would have a material adverse effect on our financial condition and results of operations.

Occurrence of any change of control could cause us to make an offer to repurchase the 2016 Bonds and 2017 Bonds.

Under the terms of both of the 2016 Bonds and 2017 Bonds, at any time following the occurrence of a change of control event, we will be required to make an offer to repurchase all or, at the bondholder’s option, any part (equal to RMB1,000,000 or multiples of RMB100,000 in excess thereof), of each bondholder’s bonds at 101% of the aggregate principal amount of the bonds repurchased plus accrued and unpaid interest, if any, on the bonds repurchased. If such a change of control event were to occur, we may not have sufficient cash and may not

be able to arrange financing to redeem the bonds in time, or on acceptable terms, or at all. Failure to repay, repurchase or redeem tendered bonds by us would constitute an event of default under the bonds, which would have a material adverse effect on our financial condition and results of operations.

If we are unable to comply with the restrictions and covenants contained in our debt agreements, an event of default could occur under the terms of such agreements, which could cause repayment of such debt to be accelerated.

If we are unable to comply with the restrictions and covenants in our current or future debt and other agreements, there could be a default under the terms of these agreements. In the event of a default under these agreements, the holders of the debt could terminate their commitments to lend to us, accelerate the debt and declare all amounts borrowed due and payable or terminate the agreements, whichever the case may be.

Furthermore, some of our debt agreements, including the 2016 Bonds and 2017 Bonds, may contain cross-acceleration or cross-default provisions. As a result, our default under one debt agreement may cause the acceleration of debt, including the 2016 Bonds and 2017 Bonds, or result in a default under our other debt agreements, including the 2016 Bonds and 2017 Bonds. If any of these events occur, we cannot assure you that our assets and cash flow would be sufficient to repay in full all of our indebtedness, or that we would be able to find alternative financing. Even if we could obtain alternative financing, we cannot assure you that it would be on terms that are favorable or acceptable to us.

Increased power costs and limited availability of electrical resources may adversely affect our results of operations.

Costs of power account for a significant portion of our overall costs for both our self-built data centers and partnered data centers. We may not be able to pass on increased power costs to our customers, which could harm our results of operations. Power and cooling requirements at our data centers are also increasing as a result of the increasing power demands of today’s servers. Since we rely on third parties to provide our data centers with power, our data centers could have a limited or inadequate access to power. Our customers’ demand for power may also exceed the power capacity in our older data centers, which may limit our ability to fully utilize these data centers. This could adversely affect our relationships with our customers, which could harm our business and have an adverse effect on our results of operations.

If we are unable to manage our growth effectively, our financial results could suffer.

The growth of our business and our service offerings may strain our operating and financial resources. Furthermore, we intend to continue expanding our overall business, customer base, headcount, and operations. Managing a geographically dispersed workforce requires substantial management effort and significant additional investment in our operating and financial system capabilities and controls. If our information systems are unable to support the demands placed on them by our growth, we may need to implement new systems, which would be disruptive to our business. We may also initiate similar network upgrade in the future if required by our operations. We may be unable to manage our expenses effectively in the future due to the expenses associated with these expansions and such expansions or upgrade may cause disruption of services to our customers, which may negatively impact our net revenues and operating expenses. If we fail to improve our operational systems or to expand our customer service capabilities to keep pace with the growth of our business, we could experience customer dissatisfaction, cost inefficiencies, and lost revenue opportunities, which may materially and adversely affect our results of operations.

If we are unable to successfully identify and analyze changing market trends and adjust our growth strategies accordingly in a timely and cost-effective manner, our results of operations could be adversely affected.

As China’s internet infrastructure market remains at its early stage, especially compared to those in more advanced economies, we generally operate in a more complex business environment with changing market dynamics. On one hand, the imbalance between material growth in internet traffic and the relative limited supply

of high quality internet infrastructure services drives strong demand for not only data center services, but also complementary value-added services in adjacent markets, including network transmission services, CDN services, cloud services and VPN services, among others. On the other hand, the potential changes in competitive landscape and regulations in an otherwise highly regulated market continues to present ambiguities and challenges. Therefore, we need to evaluate, on a continuously basis, the changing market dynamics and from time to time make adjustments to our growth strategies and operations accordingly. Any material changes to our strategies and operations, including adjustments to business models, new business areas and acquisitions, are evaluated financially, strategically and operationally by the management and approved by our board of directors. However, if we fail to capture new growth opportunities, or become unsuccessful in modifying our strategies and operations to adapt to these changing market conditions in a timely and cost-effective manner, our results of operations could be materially and adversely affected.

In addition, we have and may continue to expand in new business areas that we believe either strengthen our competitive position or will improve our future growth rates. Some of these new business areas require substantial upfront investments, which may precede anticipated generation of revenues. If we fail to successfully manage the progress of these new growth initiatives or if changing market conditions prove to work against our proposed business plans, we may not be able to attract new customers and generate general revenues and profits as anticipated, which could materially and adversely affect our results of operations.

If we are unable to adapt to evolving technologies and customer demands in a timely and cost-effective manner, our ability to sustain and grow our business may suffer.

To be successful, we must adapt to our rapidly changing market by continually improving the performance, features, and reliability of our services and modifying our business strategies accordingly. We could also incur substantial costs if we need to modify our services or infrastructure in order to adapt to these changes. We may not be able to timely adapt to changing technologies, if at all. Our ability to sustain and grow our business would suffer if we fail to respond to these changes in a timely and cost-effective manner. New technologies or industry standards have the potential to replace or provide lower cost alternatives to our data center services. The adoption

of such new technologies or industry standards could render some or all of our services obsolete or unmarketable. We cannot guarantee that we will be able to identify the emergence of all of these new service alternatives successfully, modify our services accordingly, or develop and bring new products and services to market in a timely and cost-effective manner to address these changes. If and when we do identify the emergence of new service alternatives and introduce new products and services to market, those new products and services may need to be made available at lower price points than our then-current services. Failure to provide services to compete with new technologies or the obsolescence of our services could lead us to lose current and potential customers or could cause us to incur substantial costs, which would harm our results of operations and financial condition. Our introduction of new alternative products and services that have lower price points than current offerings may result in our existing customers switching to the lower cost products, which could reduce our revenues and have a material adverse effect of our results of operations.

We have expanded to the cloud services market for a short period of time and failure to successfully grow our cloud service business will have a material and adverse effect on our growth, results of operations and business prospects.

WeThrough our strategic partnership with Microsoft, we started providing public cloud servicesservice in 2013 through our partnership with Microsoft, and hybrid cloud service in 2014. We further expanded to provide private cloud and hybrid services through our partnership with IBM in 2014. Cloud services are a new and emerging market in China and we have limited experience in this market. Our success in the cloud service business is subject to various risks and uncertainties, including:

If we are unable to effectively manage these risks, we may not be able to successfully operate in the cloud services market and achieve the expected growth.

In addition, the expansion into the cloud services market has resulted in a change to our business, including, among others, the change of our customer base. Although we derived over a majority of our revenues in 2013 from customers in China’s internet industry, theThe number of enterprise and government entity customers has increased with our expansion into the cloud services market. Our lack of experience in dealing with enterprise and government entity customers may pose new challenges for us. We may not be able to manage our business growth strategy as planned and our results of operations and business prospects may be materially and adversely affected.

If we fail to maintain a strong brand name, we may lose our existing customers and have difficulties attracting new customers, which may have an adverse effect on our business and results of operation.

We have built a strong brand in Chinese, “ ”, among our customers. As our business grows, we plan to continue to focus our efforts to establish a wider recognition of our brand to attract potential customers. We cannot assure you that we will effectively allocate our resources for these activities or succeed in maintaining and broadening our brand recognition among customers. Our major brand names and logos are registered trademarks in China. However, preventing trademark and trade name infringement or misuse could be difficult, costly and time-consuming, particularly in China. There had been incidents in the past where third parties used our brand without our authorization and we had to resort to litigation to protect our intellectual property rights. See “Item 8.A—Legal Proceedings” for our disputes with Shanghai 21Vianet Information Systems Co., Ltd. We may continue to experience similar disputes in the future or otherwise fail to fully protect our brand name, which may have an adverse effect on our business and financial results.

Any negative publicity and allegations against us may adversely affect our brand, public image and reputation, which may harm our ability to attract and retain users and business partners and result in material adverse impact on our business, results of operations and prospects.

Negative publicity and allegations about us, our products and services, our financial results or our market position in general, including by short sellers or investment research firms, regardless of their veracity, may adversely damage our brand, public image and reputation, harm our ability to attract and retain users and result in material adverse impact on our share price, business, results of operations and prospects. For example, on September 10, 2014, Trinity Research Group, or Trinity, a short seller that was allegedly formed in 2014, issued a report alleging that we operate through a Ponzi scheme and have reported fraudulent financials and operating metrics. On September 17, 2014, Trinity issued a second report. The trading price of our ADSs declined and two

shareholder class action lawsuits were filed against us and some of our directors and senior executive officers. See “Item 8.A—Legal Proceedings” for more information on the two shareholder class action lawsuits. Through two separate, comprehensive rebuttal reports, we have rejected all the allegations set out in the Trinity reports and are prepared to defend ourselves in the shareholder class action lawsuits, but our share price fluctuated after such negative publicity.

Rapid urbanization and changes in zoning and urban planning in China may cause our leased properties to be demolished, removed or otherwise affected.

China is undergoing a rapid urbanization process, and zoning requirements and other governmental mandates with respect to urban planning of a particular area may change from time to time. When there is a change in zoning requirements or other governmental mandates with respect to the areas where our data centers are located, the affected data centers may need to be demolished and removed. As a result, we may have to relocate our data centers to other locations. We have not experienced such demolition and relocation in the past, but we cannot assure you that we will not experience demolitions or interruptions of our data center operations due to zoning or other local regulations. Any such demolition and relocation could cause us to lose primary locations for our data centers and we may not be able to achieve comparable operation results following the relocations. While we may be reimbursed for such demolition and relocation, we cannot assure you that the reimbursement, as determined by the relevant government authorities, will be sufficient to cover our direct and indirect losses. Accordingly, our business, results of operations and financial condition may be materially and adversely affected.

Our business depends substantially on the continuing efforts of our executives, and our business may be severely disrupted if we lose their services.

Our future success heavily depends upon the continued services of our executives and other key employees. In particular, we rely on the expertise and experience of Sheng Chen, our co-founder, chairman of the board of directors and chief executive officer. We rely on their industry expertise, their experience in our business operations and sales and marketing, and their working relationships with our employees, our other major shareholders, our clients and relevant government authorities. If one or more of our senior executives were unable or unwilling to continue in their present positions, we might not be able to replace them easily or at all. If any of our senior executives joins a competitor or forms a competing company, we may lose clients, suppliers, key professionals and staff members. Each of our executive officers has entered into an employment agreement with us, which contains non-competition provisions. However, if any dispute arises between our executive officers and us, we cannot assure you the extent to which any of these agreements could be enforced in China, where these executive officers reside, in light of the uncertainties with China’s legal system. See “—Risks Related to Doing Business in China—Uncertainties with respect to the PRC legal system could limit legal protections available to you and us.”

If we are unable to recruit or retain qualified personnel, our business could be harmed.

We must continue to identify, hire, train, and retain IT professionals, technical engineers, operations employees, and sales and management personnel who maintain relationships with our customers and who can provide the technical, strategic, and marketing skills required for our company to grow. There is a shortage of qualified personnel in these fields, and we compete with other companies for the limited pool of these personnel. Any

failure to recruit and retain necessary technical, managerial, sales, and marketing personnel, including but not limited to members of our executive team, could harm our business and our ability to grow.

Our managed network services business may fluctuate or decline.

Although managed network services are one of our core competencies in our overall service offerings as a comprehensive infrastructure provider in China, our managed network service business has been and will likely remain a relatively more volatile portion of our overall revenue base. As the managed network services market

continues to evolve and as we further optimize our growth strategies and allocate resources to more attractive areas with higher growth and return rates, we may become more selective in pursuing future revenue opportunities in the managed network services business. In addition, we have experienced pricing pressure for our managed network services in recent years and we expect that this trend may continue. Therefore, revenues from managed network services could experience decline both in the absolute amount and as a percentage of our consolidated revenues, which could have a negative impact on our overall growth and profitability.

The uncertain economic environment may continue to have an adverse impact on our business and financial condition.

The uncertain economic environment could have an adverse effect on our liquidity. While we believe we have a strong customer base, if the current market conditions were to worsen, some of our customers may have difficulty paying us and we may experience increased churn in our customer base and reductions in their commitments to us. WeAs of the date of this annual report, we have not experienced any of the foregoing; however, if these circumstances do occur, we may also be required to further increase our allowance for doubtful accounts and our results would be negatively impacted. Our sales cycle could also be lengthened if customers slow spending, or delay decision-making, on our products and services, which could adversely affect our revenues growth and our ability to recognize revenue. Finally, we could also experience pricing pressure as a result of economic conditions if our competitors lower prices and attempt to lure away our customers with lower cost solutions. Finally, our ability to access the capital markets may be severely restricted at a time when we would like, or need, to do so which could have an impact on our flexibility to pursue additional expansion opportunities and maintain our desired level of revenue growth in the future.

Our results of operations have fluctuated and may continue to fluctuate, which could make our future results difficult to predict. This may also result in significant volatility in, and otherwise adversely affect, the market for our ADSs.

Our results of operations have fluctuated and may continue to fluctuate due to a variety of factors, including many of the risks described in this section, which are outside of our control. As a result, comparing our results of operations on a period-to-period basis may not be meaningful. You should not rely on our results of operations for any prior periods as an indication of our future operating performance. Fluctuations in our revenue can lead to even greater fluctuations in our results of operations. Our budgeted expense levels depend in part on our expectations of long-term future revenue. Given relatively fixed operating costs related to our personnel and facilities, any substantial adjustment to our expenses to account for lower than expected levels of revenue will be difficult and time consuming. Consequently, if our revenues do not meet projected levels, our operating performance will be negatively affected. Fluctuations in our results of operations could result in significant volatility in, and otherwise.otherwise adversely affect, the market for our ADSs.

If we fail to maintain an effective system of internal control over financial reporting, we may be unable to accurately report our financial results or prevent fraud, and investor confidence in our company and the market price of our ADSs may be adversely affected.

The SEC, as required by Section 404 of the Sarbanes-Oxley Act of 2002, or the Sarbanes-Oxley Act, adopted rules requiring most public companies to include a management report on such company’s internal control over financial reporting in its annual report, which contains management’s assessment of the effectiveness of the company’s internal control over financial reporting. In addition, when a company meets the SEC’s criteria, an independent registered public accounting firm must report on the effectiveness of the company’s internal control over financial reporting.

Our management and independent registered public accounting firm have concluded that our internal control over financial reporting as of December 31, 20132014 was effective. Our management’s assessment of and conclusion on the effectiveness of internal control over financial reporting did not include the internal controls of SC Aipu

and Dermot Holding Limited, which are included in our 2014 consolidated financial statements and constituted RMB3,443.9 million and RMB2,513.0 million of total and net assets, respectively, as of December 31, 2014 and RMB578.3 million and RMB50.8 million of revenues and net income, respectively, for the year then ended. Our independent registered public accounting firm’s audit of our internal control over financial reporting also did not include an evaluation of the internal control over financial reporting of SC Aipu and Dermot Holding Limited.

However, we cannot assure you that in the future our management or our independent registered public accounting firm will not identify material weaknesses during the Section 404 of the Sarbanes-Oxley Act audit process or for other reasons. In addition, because of the inherent limitations of internal control over financial reporting, including the possibility of collusion or improper management override of controls, material misstatements due to error or fraud may not be prevented or detected on a timely basis. As a result, if we fail to maintain effective internal control over financial reporting or should we be unable to prevent or detect material misstatements due to error or fraud on a timely basis, investors could

lose confidence in the reliability of our financial statements, which in turn could harm our business, results of operations and negatively impact the market price of our ADSs, and harm our reputation. Furthermore, we have incurred and expect to continue to incur considerable costs and to use significant management time and other resources in an effort to comply with Section 404 and other requirements of the Sarbanes-Oxley Act.

Compliance with rules and regulations applicable to companies publicly listed in the United States is costly and complex and any failure by us to comply with these requirements on an ongoing basis could negatively affect investor confidence in us and cause the market price of our ADSs to decrease.

In addition to Section 404, the Sarbanes-Oxley Act also mandates, among other things, that companies adopt corporate governance measures, imposes comprehensive reporting and disclosure requirements, sets strict independence and financial expertise standards for audit committee members, and imposes civil and criminal penalties for companies, their chief executive officers, chief financial officers and directors for securities law violations. For example, in response to the Sarbanes-Oxley Act, NASDAQ has adopted additional comprehensive rules and regulations relating to corporate governance. These laws, rules and regulations have increased the scope, complexity and cost of our corporate governance and reporting and disclosure practices. Our current and future compliance efforts will continue to require significant management attention. In addition, our board members, chief executive officer and chief financial officer could face an increased risk of personal liability in connection with the performance of their duties. As a result, we may have difficulty attracting and retaining qualified board members and executive officers to fill critical positions within our company. Any failure by us to comply with these requirements on an ongoing basis could negatively affect investor confidence in us, cause the market price of our ADSs to decrease or even result in the delisting of our ADSs from NASDAQ.

We are subject to China’s anti-corruption laws and the U.S. Foreign Corrupt Practices Act. Our failure to comply with these laws could result in penalties, which could harm our reputation and have an adverse effect on our business, results of operations and financial condition.

We are subject to the U.S. Foreign Corrupt Practices Act, or the FCPA, which generally prohibits companies and anyone acting on their behalf from offering or making improper payments or providing benefits to foreign officials for the purpose of obtaining or keeping business, along with various other anti-corruption laws, including China’s anti-corruption laws. Our existing policies prohibit any such conduct and we are in the process of implementing additional policies and procedures designed to ensure that we, our employees and intermediaries comply with the FCPA and other anti-corruption laws to which we are subject. There is, however, no assurance that such policies or procedures will work effectively all the time or protect us against liability under the FCPA or other anti-corruption laws for actions taken by our employees and intermediaries with respect to our business or any businesses that we may acquire. We operate in the data center services industry in China and generally purchase our hosting facilities and telecommunications resources from state or government-owned enterprises and sell our services domestically to customers that include state or government-owned enterprises or government ministries, departments and agencies. This puts us in frequent contact with persons who may be

considered “foreign officials” under the FCPA, resulting in an elevated risk of potential FCPA violations. If we are found to be not in compliance with the FCPA and other applicable anti-corruption laws governing the conduct of business with government entities or officials, we may be subject to criminal and civil penalties and other remedial measures, which could have an adverse impact on our business, financial condition and results of operations. Any investigation of any potential violations of the FCPA or other anti-corruption laws by U.S. or foreign authorities, including Chinese authorities, could adversely impact our reputation, cause us to lose customer sales and access to hosting facilities and telecommunications resources, and lead to other adverse impacts on our business, financial condition and results of operations.

If we fail to protect our intellectual property rights, our business may suffer.

We consider our copyrights, trademarks, trade names and internet domain names invaluable to our ability to continue to develop and enhance our brand recognition. Historically, the PRC has afforded less protection to

intellectual property rights than the United States. We utilize proprietary know-how and trade secrets and employ various methods to protect such intellectual property. Unauthorized use of our copyrights, trademarks, trade names and domain names may damage our reputation and brand. Preventing copyright, trademark and trade name infringement or misuse could be difficult, costly and time-consuming, particularly in China. The measures we take to protect our copyrights, trademarks and other intellectual property rights are currently based upon a combination of trademark and copyright laws in China and may not be adequate to prevent unauthorized uses. Furthermore, application of laws governing intellectual property rights in China is uncertain and evolving, and could involve substantial risks to us. If we are unable to adequately protect our trademarks, copyrights and other intellectual property rights in the future, we may lose these rights, our brand name may be harmed, and our business may suffer materially. Furthermore, our management’s attention may be diverted by violations of our intellectual property rights, and we may be required to enter into costly litigation to protect our proprietary rights against any infringement or violation.

We may face intellectual property infringement claims that could be time-consuming and costly to defend. If we fail to defend ourselves against such claims, we may lose significant intellectual property rights and may be unable to continue providing our existing services.

Our technologies and business methods, including those relating to data center services, may be subject to third-party claims or rights that limit or prevent their use. Companies, organizations or individuals, including our competitors, may hold or obtain patents or other proprietary rights that would prevent, limit or interfere with our ability to make, use or sell our services or develop new services, which could make it more difficult for us to operate our business. Intellectual property registrations or applications by others relating to the type of services that we provide may give rise to potential infringement claims against us. In addition, to the extent that we gain greater visibility and market exposure as a public company, we are likely to face a higher risk of being subject to intellectual property infringement claims from third parties. We expect that infringement claims may further increase as the number of products, services and competitors in our market increases. Further, continued success in this market may provide an impetus to those who might use intellectual property litigation as a tool against us.

It is critical that we use and develop our technology and services without infringing the intellectual property rights of third parties, including but not limited to patents, copyrights, trade secrets and trademarks. Intellectual property litigation is expensive and time-consuming and could divert management’s attention from our business. A successful infringement claim against us, whether with or without merit, could, among others things, require us to pay substantial damages, develop non-infringing technology or enter into royalty or license agreements that may not be available on acceptable terms, if at all, and cease making, licensing or using products that have infringed a third party’s intellectual property rights. Protracted litigation could also result in existing or potential customers deferring or limiting their purchase or use of our products until resolution of such litigation, or could require us to indemnify our customers against infringement claims in certain instances. Any intellectual property litigation could have a material adverse effect on our business, results of operations or financial condition.

If we fail to defend ourselves against any intellectual property infringement claim, we may lose significant intellectual property rights and may be unable to continue providing our existing services, which could have a material adverse effect on our results of operations and business prospects.

We have granted, and may continue to grant, stock options and other forms of share-based incentive awards, which may result in significant share-based compensation expenses.

As of the date of this annual report, we have options to purchase 10,926,3198,067,824 ordinary shares and 1,086,0933,575,395 RSUs, issued and outstandinghave been granted under our 2010 share incentive plan.plan, or the 2010 Plan, and 2014 share incentive plan, or the 2014 Plan. See “Item 6.B—Compensation of Directors and Executive Officers—Share Incentive Plan.Plans.” For the year ended December 31, 2013,2014, we recorded RMB67.8RMB233.7 million (US$11.237.7 million) in share-based compensation expenses.expenses, including RMB116.5 million (US$18.8 million) in connection with options and RSUs granted under our 2010 Plan and 2014 Plan and RMB117.2 million (US$18.9 million) for the fully vested ADSs issued to Galaxy ENet Inc., or Galaxy ENet, a company owned by a certain management employee of the Managed Network Entities. These ADSs are to compensate certain management employees of the Managed Network Entities in exchange for their past services and all of them have transferred their rights to Galaxy ENet. We believe share-based incentive awards enhance our ability to attract and retain key personnel and employees, and we will continue to grant stock options, RSUs and other share-based awards to employees in the future. If our share-based compensation expenses continue to be significant, our results of operations would be materially and adversely affected.

Furthermore, in 2010, we recorded RMB206.1 million of share-based compensation expenses in connection with 24,826,090 fully-vested ordinary shares issued to Sunrise Corporate Holding Ltd., or Sunrise, a company solely owned by our chairman and chief executive officer. Subsequently, in July 2012, we repurchased 2,686,965 shares from Sunrise at par value, for the purpose of increasing the maximum aggregate number of shares available for grant under our 2010 share incentive planPlan by the same amount. We may record share-based compensation expense for a portion or all of the shares that are held by Sunrise or the shares that were added to our 2010 share incentive plan,Plan, as amended, again at significantly different values if our chairman and chief executive officer decides at a future date to transfer a portion of these shares to existing and former employees of our company. Any share-based shareholder contribution, if and when made by our chairman and chief executive officer for the benefit of our company, would be required to be recognized as share-based compensation expenses within our results of operations, which would be derived from the estimated fair value of the ordinary share award on the transfer date. Our future results of operations may be materially and adversely affected if a significant amount of share-based compensation is recorded in connection with such future transfers of these ordinary shares.

We may not have adequate insurance coverage to protect us from potential losses.

Our operations are subject to hazards and risks normally associated with daily operations for our data centers. Currently, we maintain insurance policies for our equipment, but we do not maintain any business interruption insurance or third-party liability insurance. Insurance companies in China currently do not offer as extensive an array of insurance products as insurance companies do in more developed economies. The occurrence of any events not covered by our limited insurance coverage may result in interruption of our operations and subject us to significant losses or liabilities. In addition, any losses or liabilities that are not covered by our current insurance policies or are not insured at all may have a material adverse effect on our business, results of operations and financial condition.

We face risks related to natural disasters, health epidemics and other outbreaks, which could significantly disrupt our operations.

Our business could be materially and adversely affected by natural disasters or public health emergencies, such as the outbreak of avian influenza, severe acute respiratory syndrome, or SARS, or another epidemic. On May 12, 2008 and April 14, 2010, severe earthquakes hit part of Sichuan province in southeastern China and part of Qinghai province in western China, respectively, resulting in significant casualties and property damage.

While we did not suffer any loss or experience any significant increase in cost resulting from these earthquakes, if a similar disaster were to occur in the future that affected Beijing or another city where we have major operations, our operations could be materially and adversely affected due to loss of personnel and damages to property. In addition, a similar disaster affecting a larger, more developed area could also cause an increase in our costs resulting from the efforts to resurvey the affected area. Even if we are not directly affected, such a disaster could affect the operations or financial condition of our customers and suppliers, which could harm our results of operations.

In addition, our business could be materially and adversely affected by natural disasters or public health emergencies, such as the outbreak of avian influenza, severe acute respiratory syndrome, or SARS, Ebola virus, or another epidemic. In April 2009, a new strain of influenza A virus subtype H1N1, commonly referred to as “swine flu,” was first discovered in North America and quickly spread to other parts of the world, including China. In early June 2009, the World Health Organization, or the WHO, declared the outbreak to be a pandemic, while noting that most of the illnesses were of moderate severity. The PRC Ministry of Health has reported several hundred deaths caused by influenza A (H1N1). In March 2013, a new virus subtype H7N9, commonly known as “bird flu” or “avian flu,” was discovered in eastern China. In April 2013, the WHO has identified H7N9 as “an unusually dangerous virus for humans” but the number of cases detected after April 2013 fell abruptly. A total of 139 laboratory-confirmed human cases with H7N9 virus infection including 45 deaths were reported to the WHO as of November 6, 2013. Any outbreak of avian flu, SARS, influenza A (H1N1), or their variations, or other adverse public health epidemic in China may have a material and adverse effect on our business operations. These occurrences could require the temporary closure of our offices or prevent our staff from traveling to our customers’ offices to provide on-site services. Such closures could severely disrupt our business operations and adversely affect our results of operations.

Our independent registered public accounting firm, like other independent registered public accounting firms operating in China, is not permitted to be subject to inspection by the Public Company Accounting Oversight Board and, as such, you are deprived of the benefits of such inspection.

Our independent registered public accounting firm that issues the audit reports included in our annual reports filed with the U.S. Securities and Exchange Commission, or SEC, as auditors of companies that are traded publicly in the United States and a firm registered with the U.S. Public Company Accounting Oversight Board (United States), or the PCAOB, is required by the laws of the United States to undergo regular inspections by the PCAOB to assess its compliance with the laws of the United States and professional standards. Because our auditors are located in the People’s Republic of China, a jurisdiction where the PCAOB is currently unable to conduct inspections without the approval of the Chinese authorities, our auditors are currently not inspected by the PCAOB. In May 2013, PCAOB announced that it had entered into a Memorandum of Understanding on Enforcement Cooperation with the CSRC and the Ministry of Finance, which establishes a cooperative framework between the parties for the production and exchange of audit documents relevant to investigations undertaken by PCAOB, the China Securities Regulatory Commission, or the CSRC, or the Ministry of Finance in the United States and the PRC, respectively. PCAOB continues to be in discussions with the CSRC and the Ministry of Finance to permit joint inspections in the PRC of audit firms that are registered with PCAOB and audit Chinese companies that trade on U.S. exchanges.

Inspections of other firms that the PCAOB has conducted outside China have identified deficiencies in those firms’ audit procedures and quality control procedures, which may be addressed as part of the inspection process to improve future audit quality. This lack of the PCAOB inspections in China prevents PCAOB from regularly evaluating our auditor’s audits and its quality control procedures. As a result, investors may be deprived of the benefits of PCAOB inspections.

The inability of the PCAOB to conduct inspections of auditors in China makes it more difficult to evaluate the effectiveness of our auditor’s audit procedures or quality control procedures as compared to auditors outside of China that are subject to PCAOB inspections. Investors may lose confidence in our reported financial information and procedures and the quality of our financial statements, which may have a material adverse effect on our ADS price.

Proceedings instituted recently by the SEC against five PRC-based accounting firms, including our independent registered public accounting firm, could result in our financial statements being determined to not be in compliance with the requirements of the Exchange Act.

In late 2012, the SEC commenced administrative proceedings under Rule 102(e) of its Rules of Practice and also under the Sarbanes-Oxley Act of 2002 against the Chinese affiliates of the “big four”‘‘big four’’ accounting firms, (including our auditors) and also against Dahua (the former BDO affiliate in China). The Rule 102(e) proceedings initiated by the SEC relate to these firms’ inability to produce documents, including audit work papers, in response to the request of the SEC pursuant to Section 106 of the Sarbanes-Oxley Act of 2002, as the auditors located in the PRC are not in a position lawfully to produce documents directly to the SEC because of restrictions under PRC law and specific directives issued by the China Securities Regulatory Commission. The issues raised by the proceedings are not specific to our auditors or to us, but affect equally all audit firms based in China and all China-based businesses with securities listed in the United States.

In January 2014, the administrative judge reached an Initial Decisioninitial decision that the “big four” accounting firms should be barred from practicing before the Commission for six months. However, it is currently impossible to determine the ultimate outcome of this matter as theThe “big four” accounting firms have filed a petition for reviewappealed the initial administrative law decision to the SEC in February 2014. In February 2015, each of the Initial Decision and pending that review the effect of the Initial Decision is suspended. The SEC Commissioners will review the Initial Decision, determine whether there has been any violation and, if so, determine the appropriate remedy to be placed on these audit firms. Once such an order was made, the“big four” accounting firms would haveagreed to a further rightcensure and to appealpay a fine to the US Federal courts,SEC to settle the dispute and avoid suspension of their ability to practice before the effect ofSEC. The settlement requires the order might be further stayed pendingfirms to follow detailed procedures to seek to provide the outcome ofSEC with access to Chinese firms’ audit documents via China Securities Regulatory Commission. If the firms do not follow these procedures, the SEC could impose penalties such as suspensions, or it could restart the administrative proceedings.

In the event that appeal.

Dependingthe SEC restarts the administrative proceedings, depending upon the final outcome, listed companies in the United States with major PRC operations may find it difficult or impossible to retain auditors in respect of their operations in the PRC, which could result in financial statements being determined to not be in compliance with the requirements of the Securities Exchange Act of 1934, as amended, or the Exchange Act, including possible delisting. Moreover, any negative news about the proceedings against these audit firms may cause investor uncertainty regarding China-based, United States-listed companies and the market price of our ADSs may be adversely affected.

If our independent registered public accounting firm were denied, even temporarily, the ability to practice before the SEC and we were unable to timely find another registered public accounting firm to audit and issue an opinion on our financial statements, our financial statements could be determined not to be in compliance with the requirements of the Exchange Act. Such a determination could ultimately lead to the delay or abandonment of this offering, delisting of our ordinary shares from the Nasdaq Global Select Market or deregistration from the SEC, or both, which would substantially reduce or effectively terminate the trading of our ADSs in the United States.

Risks Related to Our Corporate Structure

If the PRC government finds that the arrangements that establish the structure for operating our business do not comply with PRC government restrictions on foreign investment in the telecommunications business or if these regulations or the interpretation of existing regulations change in the future, we could be subject to severe penalties or be forced to relinquish our interests in those operations.

The PRC government regulates telecommunications-related businesses through strict business licensing requirements and other government regulations. These laws and regulations also include limitations on foreign ownership of PRC companies that engage in telecommunications-related businesses. Specifically, foreign investors are not allowed to own more than a 50% equity interest in any PRC company engaging in value-added telecommunications businesses.

Because we are a Cayman Islands company, we are classified as a foreign enterprise under PRC laws and regulations, and our wholly-owned PRC subsidiaries, 21Vianet Data Center Co., Ltd., or 21Vianet China, and Suzhou Zhuoaiyi Information Technology

Joytone Infotech Co., Ltd., or SuzhouSZ Zhuoaiyi, and Abitcool (China) Broadband Inc., or aBitCool DG, are foreign-invested enterprises.enterprises, or FIEs. To comply with PRC laws and regulations, we conduct our business in China through contractual arrangements with our variable interest entities and their shareholders. These contractual arrangements provide us with effective control over our variable interest entities, and enable us to receive substantially all of the economic benefits of our consolidated affiliated entities in consideration for the services provided by our wholly-owned PRC subsidiaries, and have an exclusive option to purchase all of the equity interest in our variable interest entities when permissible under PRC laws. For a description of these contractual arrangements, see “Item 7.B—Related Party Transaction—Transactions—Contractual Arrangements with Our Variable Interest Entities.Entities and Their Shareholders.”

The Ministry of Industry and Information Technology, or the MIIT, issued a circular in July 2006 requiring foreign investors to set up a foreign-invested enterprisean FIE and obtain a value-added telecommunications business operating license, or the VAT License, in order to conduct any value-added telecommunications business in China. Pursuant to this circular, a domestic license holder is prohibited from leasing, transferring or selling the license to foreign investors in any form, and from providing any assistance, including resources, sites or facilities, to foreign investors that conduct value-added telecommunications business in China illegally. Furthermore, the relevant trademarks and domain names that are used in the value-added telecommunications business must be owned by the local license holder or its shareholder. The circular further requires each license holder to have the necessary facilities for its approved business operations and to maintain such facilities in the regions covered by its license. In addition, all value-added telecommunications service providers are required to maintain network and information security in accordance with the standards set forth under relevant PRC regulations. DueCompanies in violation of the circular will be ordered by relevant authorities to take remedial actions within a lackspecific period and licenses may be withdrawn if such remedial actions cannot be completed within the specific period. As of interpretations from the MIIT,date of this annual report, we have not been notified by relevant authorities regarding any violation of the circular when conducting our value-added telecommunications business, and it is unclear what impact this circular will have on us or other similarly situated companies.companies as the circular is in the process of being amended.

We believe that we comply with the current applicable PRC laws and regulations. King & Wood Mallesons,Beijing DHH Law Firm, our PRC legal counsel, based on its understanding of the relevant laws and regulations, is of the opinion that each of the contracts among us, our wholly-owned PRC subsidiaries, our variable interest entities and their shareholders is valid, legally binding and enforceable upon each party of such agreements under PRC laws and regulations, and will not result in any violation of PRC laws or regulations currently in effect. However, as there are substantial uncertainties regarding the interpretation and application of PRC laws and regulations, including the Regulations on Mergers and Acquisitions of Domestic Enterprises by Foreign Investors, or the M&A Rules, the telecommunications circular described above and the Telecommunications Regulations and the relevant regulatory measures concerning the telecommunications industry, therefore, we cannot assure you that the PRC government that regulate providers of data center service and other participants in the telecommunications industry would agree that our corporate structure or any of the above contractual arrangements comply with PRC licensing, registration or other regulatory requirements, with existing policies or with requirements or policies that may be adopted in the future. PRC laws and regulations governing the validity of these contractual arrangements are uncertain and the relevant government authorities have broad discretion in interpreting these laws and regulations.

If our corporate and contractual structure is deemed by the MIIT, or other regulators having competent authority, to be illegal, either in whole or in part, we may lose control of our consolidated affiliated entities and have to modify such structure to comply with regulatory requirements. However, we cannot assure you that we can achieve this without material disruption to our business. Further, if our corporate and contractual structure is found to be in violation of any existing or future PRC laws or regulations, the relevant regulatory authorities would have broad discretion in dealing with such violations, including:

Furthermore, in connection with litigation, arbitration or other judicial or dispute resolution proceedings, assets under the name of any of record holder of equity interest in our variable interest entities, including such equity interest, may be put under court custody. As a consequence, we cannot be certain that the equity interest will be disposed pursuant to the contractual arrangement or ownership by the record holder of the equity interest. In addition, new PRC laws, rules and regulations may be introduced to impose additional requirements that may be applicable to our corporate structure and contractual arrangements. Occurrence of any of these events could materially and adversely affect our business, financial condition and results of operations. In addition, if the imposition of any of these penalties or requirement to restructure our corporate structure causes us to lose the rights to direct the activities of our variable interest entities or our right to receive their economic benefits, we would no longer be able to consolidate such variable interest entities. However, we do not believe that such actions would result in the liquidation or dissolution of our company, our wholly-owned subsidiaries in China or our variable interest entities or their subsidiaries. For the years ended December 31, 2011, 2012, 2013 and 2013,2014, our consolidated affiliated entities contributed substantially all of our total net revenues.

Our contractual arrangements with our variable interest entities may result in adverse tax consequences to us.

We could face material and adverse tax consequences if the PRC tax authorities determine that our contractual arrangements with our variable interest entities were not made on an arm’s length basis and may adjust our income and expenses for PRC tax purposes by requiring a transfer pricing adjustment. A transfer pricing adjustment could adversely affect us by (i) increasing the tax liabilities of our variable interest entities without reducing their respective tax liability, which could further result in late payment fees and other penalties to our variable interest entities for underpaid taxes; or (ii) limiting the ability of our variable interest entities to obtain or maintain preferential tax treatments and other financial incentives.

We rely on contractual arrangements with our variable interest entities and their shareholders for our China operations, which may not be as effective as direct ownership in providing operational control.

We rely on contractual arrangements with our variable interest entities and their shareholders to operate our business in China. For a description of these contractual arrangements, see “Item 7.B—Related Party Transaction—Transactions—Contractual Arrangements with Our Variable Interest Entities.Entities and Their Shareholders.” Substantially all of our revenues and cash flows are attributed to our consolidated affiliated entities. These contractual arrangements may not be as effective as direct ownership in providing us with control over our variable interest entities. If our variable interest entities or their shareholders fail to perform their respective obligations under these contractual arrangements, our recourse to the assets held by our consolidated affiliated entities is indirect and we may have to incur substantial costs and expend significant resources to enforce such arrangements in reliance on legal

remedies under PRC law. These remedies may not always be effective, particularly in light of uncertainties in the PRC legal system.

All of these contractual arrangements are governed by PRC law and provide for the resolution of disputes through arbitration in the PRC. Accordingly, these contracts would be interpreted in accordance with PRC laws and any disputes would be resolved in accordance with PRC legal procedures. The legal environment in the PRC

is not as developed as in other jurisdictions, such as the United States. As a result, uncertainties in the PRC legal system could limit our ability to enforce these contractual arrangements. In the event that we are unable to enforce these contractual arrangements, or if we suffer significant time delays or other obstacles in the process of enforcing these contractual arrangements, it would be very difficult to exert effective control over our variable interest entities, and our ability to conduct our business and our financial conditions and results of operation may be materially and adversely affected. See “—Risks Related to Doing Business in China—Uncertainties with respect to the PRC legal system could limit legal protections available to you and us.”

The shareholders of our variable interest entities may have potential conflicts of interest with us, which may materially and adversely affect our business and financial condition.

We conduct our operations in China through contractual arrangements among us, our wholly-owned PRC subsidiaries, our variable interest entities and their shareholders and we rely on the shareholders of our variable interest entities to abide by the obligations under such contractual arrangements. For example,In particular, 21Vianet Technology is approximately 70% owned by Mr. Sheng Chen, our chairman and chief executive officer and 30% owned by Mr. Jun Zhang, our co-founder. Mr. Sheng Chen and Mr. Jun Zhang are also the ultimate shareholders of our company. The interests of Mr. Sheng Chen and Mr. Jun Zhang as the shareholders of 21Vianet Technology may differ from the interests of our company as a whole, as what is in the best interests of 21Vianet Technology may not be in the best interests of our company. We cannot assure that when conflicts of interest arise, any or all of these individuals will act in the best interests of our company or that conflicts of interest will be resolved in our favor. In addition, these individuals may breach or cause our variable interest entities and their subsidiaries to breach or refuse to renew the existing contractual arrangements with us.

Currently, we do not have arrangements to address potential conflicts of interest the shareholders of 21Vianet Technology may encounter, on one hand, and as a beneficial owner of our company, on the other hand; provided that we could, at all times, exercise our option under the optional share purchase agreement to cause them to transfer all of their equity ownership in 21Vianet Technology to a PRC entity or individual designated by us as permitted by the then applicable PRC laws. In addition, if such conflicts of interest arise, we could also, in the capacity of attorney-in-fact of the then existing shareholders of 21Vianet Technology as provided under the power of attorney, directly appoint new directors of 21Vianet Technology. We rely on the shareholders of our variable interest entities to comply with the laws of China, which protect contracts and provide that directors and executive officers owe a duty of loyalty to our company and require them to avoid conflicts of interest and not to take advantage of their positions for personal gains. We also rely on the shareholders of 21Vianet Technology, who are directors of our company, to abide bygains, and the laws of the Cayman Islands, which provide that directors have a duty of care and a duty of loyalty to act honestly in good faith with a view to our best interests. However, the legal frameworks of China and Cayman Islands do not provide guidance on resolving conflicts in the event of a conflict with another corporate governance regime. If we cannot resolve any conflicts of interest or disputes between us and the shareholders of our variable interest entities, we would have to rely on legal proceedings, which could result in disruption of our business and subject us to substantial uncertainty as to the outcome of any such legal proceedings.

Risks Related to Doing Business in China

Adverse changes in political and economic policies of the PRC government could have a material adverse effect on the overall economic growth of China, which could reduce the demand for our services and adversely affect our competitive position.

AllSubstantially all of our operations are conducted in China and substantially all of our sales are made in China. Accordingly, our business, financial condition, results of operations and prospects are affected significantly by economic, political

and legal developments in China. The PRC economy differs from the economies of most developed countries in many respects, including the amount of government involvement, the level of development, the growth rate, the control of foreign exchange and allocation of resources. While the

PRC economy has grown significantly over the past several decades, the growth has been uneven across different periods, regions and among various economic sectors of China. We cannot assure you that the PRC economy will continue to grow, or that if there is growth, such growth will be steady and uniform, or that if there is a slowdown, such a slowdown will not have a negative effect on our business.

The PRC government exercises significant control over China’s economic growth through various measures, such as allocation of resources, controlling payment of foreign currency-denominated obligations, setting monetary policy and providing preferential treatment to particular industries or companies. Some of these measures benefit the overall PRC economy, but may also have a negative effect on us. For example, our financial condition and results of operations may be adversely affected by governmental control over capital investments or changes in tax regulations that are applicable to us. In addition, it is unclear whether PRC economic policies will be effective in maintaining stable economic growth in the future. Any slowdown in China’s economic growth could lead to reduced demand for our solutions, which could in turn materially and adversely affect our business, financial condition and results of operations.

Uncertainties with respect to the PRC legal system could limit legal protections available to you and us.

We conduct substantially all of our business through our PRC subsidiaries and consolidated affiliated entities in China. Our operations in China are governed by PRC laws and regulations. Our PRC subsidiaries are foreign-invested enterprisesFIEs and are subject to laws and regulations applicable to foreign investment in China and, in particular, laws applicable to foreign-invested enterprises.FIEs. The PRC legal system is a civil law system based on written statutes. Unlike the common law system, prior court decisions may be cited for reference but are not binding.

Since late 1970s, the PRC government has been developing a comprehensive system of laws and regulations governing economic matters in general. The overall effect of legislation over the past several decades has significantly enhanced the protections afforded to various forms of foreign investments in China. However, China has not developed a fully integrated legal system, and recently enacted laws and regulations may not sufficiently cover all aspects of economic activities in China. In particular, because these laws and regulations are relatively new, and because of the limited volume of published decisions and their nonbinding nature, the interpretation and enforcement of these laws and regulations involve uncertainties. In addition, the PRC legal system is based in part on government policies and internal rules, some of which may not be published on a timely basis or at all, and some of which may have a retroactive effect. As a result, we may not be aware of our violation of these policies and rules until sometime after the violation. Any administrative and court proceedings in China may be protracted, resulting in substantial costs and diversion of resources and management attention. However, since PRC administrative and court authorities have significant discretion in interpreting and implementing statutory and contractual terms, it may be more difficult to evaluate the outcome of administrative and court proceedings and the level of legal protection we enjoy than in more developed legal systems. These uncertainties may also impede our ability to enforce the contracts we have entered into. As a result, these uncertainties could materially and adversely affect our business and results of operations.

Substantial uncertainties exist with respect to the enactment timetable, interpretation and implementation of draft PRC Foreign Investment Law and how it may impact the viability of our current corporate structure, corporate governance and business operations.

The Ministry of Commerce, or MOC, published a discussion draft of the proposed Foreign Investment Law in January 2015 aiming to, upon its enactment, replace the trio of existing laws regulating foreign investment in China, namely, the Sino-foreign Equity Joint Venture Enterprise Law, the Sino-foreign Cooperative Joint Venture Enterprise Law and the Wholly Foreign-invested Enterprise Law, together with their implementation rules and ancillary regulations. The draft Foreign Investment Law embodies an expected PRC regulatory trend to rationalize its foreign investment regulatory regime in line with prevailing international practice and the legislative efforts to unify the corporate legal requirements for both foreign and domestic investments. The MOC is currently soliciting comments on this draft and substantial uncertainties exist with respect to its enactment

timetable, interpretation and implementation. The draft Foreign Investment Law, if enacted as proposed, may materially impact the viability of our current corporate structure, corporate governance and business operations in many aspects.

Among other things, the draft Foreign Investment Law expands the definition of foreign investment and introduces the principle of “actual control” in determining whether a company should be treated as an FIE. According to the definition set forth in the draft Foreign Investment Law, FIEs refer to enterprises established in China pursuant to PRC law that are solely or partially invested by foreign investors. The draft Foreign Investment Law specifically provides that entities established in China (without direct foreign equity ownership) but “controlled” by foreign investors, through contract or trust for example, will be treated as FIEs. Once an entity falls within the definition of FIE, it may be subject to foreign investment “restrictions” or “prohibitions” set forth in a “negative list” to be separately issued by the State Council later. If an FIE proposes to conduct business in an industry subject to foreign investment “restrictions” in the “negative list,” the FIE must go through a market entry clearance by the MOC before being established. If an FIE proposes to conduct business in an industry subject to foreign investment “prohibitions” in the “negative list,” it must not engage in the business. However, an FIE, during the market entry clearance process, may apply in writing to be treated as a PRC domestic enterprise if its foreign investor(s) is/are ultimately “controlled” by PRC government authorities and its affiliates and/or PRC citizens. In this connection, “control” is broadly defined in the draft law to cover the following summarized categories: (i) holding 50% of more of the voting rights of the subject entity; (ii) holding less than 50% of the voting rights of the subject entity but having the power to secure at least 50% of the seats on the board or other equivalent decision making bodies, or having the voting power to exert material influence on the board, the shareholders’ meeting or other equivalent decision making bodies; or (iii) having the power to exert decisive influence, via contractual or trust arrangements, over the subject entity’s operations, financial matters or other key aspects of business operations.

The “variable interest entity” structure, or VIE structure, has been adopted by many PRC-based companies, including us, to obtain necessary licenses and permits in the industries that are currently subject to foreign investment restrictions in China. See “—Risks Related to Our Corporate Structure” and Item 4.C—“Organizational Structure.” Under the draft Foreign Investment Law, variable interest entities that are controlled via contractual arrangement would also be deemed as FIEs, if they are ultimately “controlled” by foreign investors. Therefore, for any companies with a VIE structure in an industry category that is on the “negative list,” the VIE structure may be deemed legitimate only if the ultimate controlling person(s) is/are of PRC nationality (either PRC companies or PRC citizens). Conversely, if the actual controlling person(s) is/are of foreign nationalities, then the variable interest entities will be treated as FIEs and any operation in the industry category on the “negative list” without market entry clearance may be considered as illegal.

To our knowledge, as of the date of this annual report, over 50% of the voting power of our issued and outstanding share capital is controlled by PRC nationals. However, the draft Foreign Investment Law has not taken a position on what actions shall be taken with respect to the existing companies with a VIE structure, whether or not these companies are controlled by Chinese parties, while it is soliciting comments from the public on this point. Moreover, it is uncertain whether the industry of data center and providing value-added telecommunication services, in which our variable interest entities operate, will be subject to the foreign investment restrictions or prohibitions set forth in the “negative list” to be issued. If the enacted version of the Foreign Investment Law and the final “negative list” mandate further actions, such as MOC market entry clearance, to be completed by companies with existing VIE structure like us, we face uncertainties as to whether such clearance can be timely obtained, or at all.

The draft Foreign Investment Law, if enacted as proposed, may also materially impact our corporate governance practice and increase our compliance costs. For instance, the draft Foreign Investment Law imposes stringent ad hoc and periodic information reporting requirements on foreign investors and the applicable FIEs. Aside from investment implementation report and investment amendment report that are required at each investment and alteration of investment specifics, an annual report is mandatory, and large foreign investors meeting certain criteria are required to report on a quarterly basis. Any company found to be non-compliant with

these information reporting obligations may potentially be subject to fines and/or administrative or criminal liabilities, and the persons directly responsible may be subject to criminal liabilities.

We may rely principally on dividends paid by our operating subsidiaries to fund cash and financing requirements, and limitations on the ability of our operating subsidiaries to make payments to us could have a material adverse effect on our ability to conduct our business and fund our operations.

We are a holding company and conduct all of our business primarily through our operating subsidiaries and our consolidated affiliated entities, most of which are limited liability companies established in China. We may rely principally on dividends paid by our subsidiaries for our cash needs, including the funds necessary to pay dividends and other cash distributions to our shareholders, to service any debt we may incur and to pay our operating expenses. The payment of dividends by entities organized in China is subject to limitations. In particular, regulations in China

currently permit payment of dividends only out of accumulated profits as determined in accordance with the PRC accounting standards and regulations. Our PRC subsidiaries are also required to set aside at least 10% of their after-tax profit based on PRC accounting standards each year to their general reserves until the accumulative amount of such reserves reaches 50% of their registered capital. These reserves are not distributable as cash dividends. Furthermore, any portion of its after-tax profits that a subsidiary has allocated to its staff welfare and bonus fund at the discretion of its board of directors is also not distributable as cash dividends. Moreover, if our operating subsidiaries incur any debt on their own behalf in the future, the instruments governing the debt may restrict their ability to pay dividends or make other distributions to us. Any limitation on the ability of our operating subsidiaries, including in particular 21Vianet China, to distribute dividends and other distributions to us could materially and adversely limit our ability to make investments or acquisitions that could be beneficial to our businesses, pay dividends or otherwise fund and conduct our business.

If we fail to acquire, obtain or maintain applicable telecommunications licenses, or are deemed by relevant governmental authorities to be operating outside the terms of our existing license, our business would be materially and adversely affected.

Pursuant to the Telecommunications Regulations promulgated by the PRC State Council in September 2000, telecommunications businesses are divided into two categories, namely, (i) “basic telecommunications businesses,” which refers to businesses that provide public network infrastructure, public data transmission and basic voice communications services, and (ii) “value-added telecommunications businesses,” which refer to businesses that provide telecommunications and information services through the public network infrastructure. If the value-added telecommunications service covers two or more provinces, autonomous regions or municipalities, such service must be approved by the MIIT and the service provider must obtain a Cross-Regional Value Added Telecommunications Business Operation License, or the Cross-Regional VAT License.

Pursuant to the Cross-Regional Value Added TechnologyVAT License issued to Beijing 21Vianet Broad Band Data Center Co., Ltd., or 21Vianet Beijing, by the MIIT on January 17, 2012 with a term effective until January 17, 2017, 21Vianet Beijing is permitted to carry out its data center business under the first category of “value-added telecommunications business” across nine cities in China.

Pursuant to the Value Added TechnologyVAT License issued to Langfang Xunchi by the Hebei Province Communications Administration, for the period from April 10, 2013 to April 10, 2017, Langfang Xunchi is permitted to carry out its data center business in Langfang and Baoding. Baoding for the period from April 10, 2013 to April 10, 2017.

Pursuant to the Value Added TechnologyVAT License issued to Beijing Chengyishidai Network Technology Co., Ltd., or CYSD, by the Beijing Communications Administration on March 30, 2012 with a term effective until June 21, 2016, CYSD is permitted to carry out its internet access service and information service (excluding fixed-line telephone information service and internet information service) business under the second category of “value-added telecommunications business” in Beijing.

Pursuant to the Value Added TechnologyVAT License issued to Guangzhou Gehua Network Technology and Development Company Limited, or Gehua, by the Guangdong Communications Administration, Gehua is permitted to carry out its internet access service business and information service business (limited to internet service business) under the second category of “value-added telecommunications business” in Guangdong province from March 29, 2013 to December 29, 2016.

Pursuant to the Cross-Regional Value Added TechnologyVAT License issued to BeijingBJ Tianwang by the MIIT on August 23, 2013 Beijingwith a term effective until January 7, 2018, BJ Tianwang is permitted to carry out its virtual private network services under the first category of “value-added telecommunications business” across 25 cities in China. Meanwhile, BeijingBJ Tianwang also holds a Value Added TechnologyVAT License issued by the Beijing Communications Administration on January 22, 2014 with a term effective until December 12, 2014, and is permitted to carry out its internet access business under the second category of “value-added telecommunications business” in Beijing. A renewed VAT License was issued to BJ Tiannang on December 31, 2014 with a term effective until December 31, 2019.

Pursuant to the Value Added TechnologyVAT License issued to BeijingBJ Yilong Xinda by the Beijing Communications Administration on October 19, 2010, BeijingBJ Yilong Xinda is permitted to carry out its information service business (limited to mobile network) under the second category of “value-added telecommunications business” in Beijing. A renewed VAT License was issued to BJ Yilong on May 22, 2014 with a term effective until October 18, 2015.

Pursuant to the Cross-Regional VAT License issued to Shenzhen Diyixian Communication Co., Ltd., or SZ DYX, by the MIIT on September 18, 2013 with a term effective until July 29, 2018, SZ DYX is permitted to carry out (i) its virtual private network services under the first category of “value-added telecommunications business” in China; and (ii) call center and information service business (limited to mobile network) under the second category of “value-added telecommunications business” across China.

Pursuant to the Cross-Regional VAT License issued to SC Aipu by the MIIT on July 31, 2012 with a term effective until August 1, 2016, SC Aipu is permitted to carry out call center and information service business (limited to mobile network) under the second category of “value-added telecommunications business” across 11 cities in China. In addition, MIIT has also approved SC Aipu to authorize each of its 5 subsidiaries to carry out internet access business under the second category of “value-added telecommunications business” in the city where such subsidiary is located.

Pursuant to the Cross-Regional VAT License issued to Shanghai Guotong Network Co., Ltd., or SH Guotong, by the MIIT on November 15, 2012, which was renewed on January 20, 2015 with a term effective until January 20, 2020, SH Guotong is permitted to carry out internet access business under the second category of “value-added telecommunications business” across 14 cities in China.

In connection with our data center services, we provide managed network services that connect our data centers with the telecommunication backbones of China’s major carriers, major non-carriers and ISPs as well as connect servers housed in our data centers. Our managed network services are offered in the form of bandwidth with optimized interconnectivity. Furthermore, we have been continuously developing our hosting service and managed network service to better serve our customers, and as a result, we introduce new technologies and

services from time to time to support and improve our current business. Besides, asAs of the date of this annual report, there is no clear and express legal definition as to what constitutes a “managed network services,” nor are there laws or regulations in China specifically governing the managed network services or categorizing it as one of the “basic telecommunications businesses” or “value-added telecommunications services. We” However, we cannot assure you that PRC governmental authorities will continue to deem our hosting service, and will deem our managed network service and any of our newly developed technologies, network and services used in our business as a type of value-added telecommunications business or a business covered under the Cross-Regional Value Added TelecommunicationsVAT License ofissued to 21Vianet Beijing, BJ Tianwang, SZ DYX, SC Aipu and SH Guotong, and the Value Added TechnologyVAT License issued to CYSD, Gehua, Langfang Xunchi, BJ Yilong and BeijingBJ Tianwang. Furthermore, we cannot assure you that PRC legislators or governmental authorities will not promulgate any new laws or regulations or update the current and existing laws

and regulations which may clearly define or categorize our managed network services as a type of basic telecommunication business. As we expand our networks across China, it is also possible that the MIIT, in the future, may deem our operations to have exceeded the terms of our existing licenses. Further, we cannot assure you that 21Vianet Beijing, CYSD, Gehua, Langfang Xunchi, BJ Tianwang, BJ Yilong, SZ DYX, SC Aipu and Beijing TianwangSH Guotong will be able to successfully renew their value added telecommunications business operating licenses upon their expiration, or maintain their annual inspection, or obtain any other licenses necessary for us to carry out our business, or that our existing licenses will continue to cover all aspects of our operations upon their renewal.

In addition, MIIT initiated a periodical pilot scheme for mobile network resale business by issuing the Notice on Carrying out Pilot Work of Mobile Network Re-sale Business on May 17, 2013, or the Pilot Work Notice, pursuant to which, the qualified private sector enterprises are encouraged, but not required, to apply to participate in the pilot scheme in mobile network resale business and the pilot scheme only lasts for a short period ending on December 31, 2015. MIIT will, according to the Pilot Work Notice, adjust relevant policies in the future as appropriate based on the result of such pilot scheme. 21Vianet Beijing has voluntarily applied to participate in the pilot scheme and obtained approval on August 18, 2014, with a term expiring on December 31, 2015.

We believe such pilot scheme represents the current administration’s continuous efforts in carrying out the recent policies of the PRC State Council and MIIT regarding encouraging private sectors to further participate in the telecommunication industry. The Pilot Work Notice specifically mentioned that the mobile network resale business, which we believe shares something in common with our managed network services, is a second-category basic telecommunication business rather than a value-added telecommunication business, and this, to some extent, reflects a legislative trend to welcome private enterprises (in comparison to the state-owned enterprise) to participate in basic telecommunication businesses in the soon future. Nevertheless, although we believe this Pilot Work Notice is not a practical change or modification to the current legal framework which our managed network service business might be subject to and it represents a legislative trend to open up the basic telecommunication business market to the private enterprises, new laws, regulations or government interpretations may also be promulgated from time to time to regulate the hosting service and managed network service or any of our related technology or services, which may require us to obtain additional, or expand existing, operating licenses or permits. Any of these factors could result in our disqualification from carrying out our current business, causing significant disruption to our business operations which may materially and adversely affect our business, financial condition and results of operations. We will be closely monitoring the developments of relevant laws and regulations.

Under the New PRC Enterprise Income Tax Law, we may be classified as a “resident enterprise” of China. Such classification could result in unfavorable tax consequences to us and our non-PRC holders of shares and ADSs.

Pursuant to the New PRC Enterprise Income Tax Law, or New EIT Law, and its implementation rules, which became effective on January 1, 2008, an enterprise established outside of China with “de facto management bodies” within China is considered a “resident enterprise,” meaning that it can be treated in a manner similar to a Chinese enterprise for enterprise income tax, or EIT, purposes. Under the implementation rules of New EIT Law, the term “de facto management body” is defined as the management body that exercises full and substantial control and overall management over the business, productions, personnel, accounts and properties of an enterprise. On April 22, 2009, the State Administration of Taxation issued the Notice Regarding the Determination of Chinese-Controlled Offshore Incorporated Enterprises as PRC Tax Resident Enterprises on the Basis of De Facto Management Bodies, or Circular 82, which is amended and supplemented by the Announcement Regarding the Determination of PRC Tax Resident Enterprises on the Basis of De Facto Management Bodies issued by the State Administration of Taxation on January 29, 2014. Circular 82 and its amendments sets out certain specific criteria and process for determining whether the “de facto management body” of a Chinese-controlled offshore incorporated enterprise is located in China. Given that the New EIT Law

and its implementation rules are relatively new and ambiguous in terms of some definitions, requirements and detailed procedures, it is unclear how tax authorities will determine tax residency based on the facts of each case.

While we believe we are not a PRC resident enterprise, we cannot ensure you that the State Administration of Taxation will not implement Circular 82 or amend the rules in the future to the effect that such rules will apply to us or our wholly-owned subsidiaries in Hong Kong. If the PRC tax authorities determine that we are a “resident enterprise” for PRC EIT purposes, a number of unfavorable PRC tax consequences could follow: (i) we may be subject to EIT at a rate of 25% on our worldwide taxable income as well as PRC EIT reporting obligations; (ii) a 10% (or a lower rate under an applicable tax treaty, if any) withholding tax may be imposed on dividends we pay to non-PRC enterprise holders (20% for non-PRC individual holders) of our shares and ADSs; and (iii) a 10% PRC tax may apply to gains realized by non-PRC enterprise holders (20% for non-PRC individual holders) of our shares and ADSs from transferring our shares or ADSs, if such income is considered PRC-source income.

Similarly, such unfavorable tax consequences could apply to our Hong Kong subsidiaries, if either of them is deemed to be a “resident enterprise” by the PRC tax authorities. Notwithstanding the foregoing provisions, the

New EIT Law also provides that the dividends paid between “qualified resident enterprises” are exempt from EIT. If our Hong Kong subsidiaries are deemed “resident enterprises” for PRC EIT purposes, the dividends they receive from their PRC subsidiaries, including 21Vianet China, may constitute dividends between “qualified resident enterprises” and therefore qualify for tax exemption. However, the definition of “qualified resident enterprise” is unclear and the relevant PRC government authorities have not yet issued guidance with respect to the processing of outbound remittances to entities that are treated as resident enterprises for PRC EIT purposes. Even if such dividends qualify as “tax-exempt income,” we cannot guarantee that such dividends will not be subject to any withholding tax.

We and our non-resident investors face uncertainty with respect to indirect transfers of equity interests in PRC resident enterprises by their non-PRC holding companies.

Pursuant to the Notice on Strengthening Administration of Enterprise Income Tax for Share Transfers by Non-PRC Resident Enterprises, or Circular 698, issued by the State Administration of Taxation, on December 10, 2009 with retroactive effect fromwhich became effective retroactively as of January 1, 2008, which is amended by the Announcement Regarding Application of Special Tax Treatment on Share Transfers by Non-PRC Resident Enterprises issued by the State Administration of Taxation on December 12, 2013, where a non-PRC residentnon-resident enterprise investor transfers the equity interests ofin a PRC resident enterprise indirectly by dispositionway of disposing of equity interests in an overseas holding company, the non-resident enterprise investor, being the transferor, may be subject to PRC enterprise income tax, if the indirect transfer is considered to be an abusive use of company structure without reasonable commercial purposes. As a result, gains derived from such indirect transfer may be subject to PRC withholding tax at the rate of up to 10%. In addition, the PRC resident enterprise may be required to provide necessary assistance to support the enforcement of Circular 698.

On February 3, 2015, the State Administration of Tax issued the Notice on Certain Corporate Income Tax Matters on Indirect Transfers of Properties by Non-Resident Enterprises, or Circular 7. Circular 7 has introduced a new tax regime that is significantly different from that under Circular 698. Circular 7 extends its tax jurisdiction to not only indirect transfers set forth under Circular 698 but also transactions involving transfer of other taxable assets, through the offshore transfer of a foreign intermediate holding company. In addition, Circular 7 provides clearer criteria than Circular 698 on how to assess reasonable commercial purposes and has introduced safe harbors for internal group restructurings and the purchase and sale of equity through a public securities market. Circular 7 also brings challenges to both the foreign transferor and transferee (or other person who is obligated to pay for the transfer) of the taxable assets. Where a non-resident enterprise conducts an “indirect transfer” by transferring the taxable assets indirectly by disposing of the equity interests of an overseas holding company, or an indirect transfer, and such overseas holding company is located in a tax jurisdiction that: (i) has an effective tax rate of less than 12.5% or (ii) does not tax foreign income of its residents, the non-PRC residentnon-resident enterprise being the transferor, mustor the transferee, or the PRC entity which directly owned the taxable assets may report this indirect transfer to the competentrelevant tax authority of the PRC resident enterprise.

such indirect transfer. Using a “substance over form” principle, the PRC tax authority may disregard the existencere-characterize such indirect transfer as a direct transfer of the overseas holding company if it lacks a reasonable commercial purposeequity interests in the PRC tax resident enterprise and was established for the purpose of reducing, avoiding or deferring PRC tax.other properties in China. As a result, gains derived from ansuch indirect transfer may be subject to PRC enterprise income tax, and the transferee or other person who is obligated to pay for the transfer is obligated to withhold the applicable taxes, currently at a rate of up to 10%. Circular 698 also provides that, where a non-PRC resident enterprise transfers its for the transfer of equity interests in a PRC resident enterpriseenterprise. Both the transferor and the transferee

may be subject to its related parties at a price lower than the fair market value, the relevant tax authority has the power to make a reasonable adjustment to the taxable income of the transaction.

There is uncertainty as to the application of Circular 698. For example, while the term “indirect transfer” is not clearly defined, it is understood that the relevantpenalties under PRC tax authorities have jurisdiction regarding requests for information overlaws if the transferee fails to withhold the taxes and the transferor fails to pay the taxes.

However, as these rules and notices are relatively new and there is a wide rangelack of foreign entities having no direct contact with China. In addition, there are not any formal declarations with regard to how to determine whether a foreign investor has adopted an abusive arrangement in order to reduce, avoid or defer PRC tax. Circular 698 may be determined byclear statutory interpretation, we face uncertainties on the tax authorities to be applicable to ourreporting and consequences on future private equity financing transactions, share exchange or other transactions involving the transfer of shares in our company by investors that are non-PRC resident enterprises, or sale or purchase of shares in other non-PRC resident companies or other taxable assets by us. Our Cayman Islands holding company and other non-PRC resident enterprises in our group may be subject to filing obligations or may be taxed if our Cayman Islands holding company and other non-PRC resident enterprises in our group are transferors in such transactions, and may be subject to withholding obligations if our Cayman Islands holding company and other non-PRC resident enterprises in our group are transferees in such transactions. For the transfer of shares in our Cayman Islands holding company by investors that are non-PRC resident enterprises, our PRC subsidiaries may be requested to assist in the filing under Circular 698 and Circular 7. As a result, we may be required to expend valuable resources to comply with these rules and notices or to request the relevant transferors from whom we purchase taxable assets to comply, or to establish that our Cayman Islands holding company and other non-resident enterprises in our group should not be taxed under Circular 698 and Circular 7, which may have a material adverse effect on our financial condition and results of operations. There is no assurance that the tax authorities will not apply Circular 698 and Circular 7 to our offshore restructuring transactions where non-residentnon-PRC resident investors were involved if any of such transactions were determined by the tax authorities to lack reasonable commercial purpose. As a result, we and our non-residentnon-PRC resident investors may be at risk of being taxed under Circular 698 and Circular 7 and may be required to expend valuable resources to comply with Circular 698 or to establish that we should not be taxed under Circular 698 and Circular 7, which may have a material adverse effect on our financial condition and results of operations or such non-residentnon-PRC resident investors’ investments in us. We have conducted acquisition transactions in the past and may conduct additional acquisition transactions in the future. We cannot assure you that the PRC tax authorities will not, at their discretion, adjust any capital gains and impose tax return filing obligations on us or require us to provide assistance for the investigation of PRC tax authorities with respect thereto. Heightened scrutiny over acquisition transactions by the PRC tax authorities may have a negative impact on potential acquisitions we may pursue in the future.

Discontinuation of any of the preferential tax treatments available to us or imposition of any additional taxes could adversely affect our financial condition and results of operations.

The New EIT Law and its implementation rules, which became effective on January 1, 2008, unified the previously-existing separate income tax laws for domestic enterprises and foreign invested enterprisesFIEs and adopted a unified 25% EIT rate applicable to all resident enterprises in China, except for certain entities established prior to March 16 that are eligible for their existing preferential tax incentives, adjusted by certain transitional phase-out rules promulgated by the State Council on December 26, 2007. In addition, certain enterprises may enjoy a preferential EIT rate of 15% under the New EIT Law if they qualify as High and New Technology Enterprise, or HNTE, subject to various qualification criteria.

In April 2009,A number of our PRC subsidiaries and consolidated affiliated entities, including 21Vianet Beijing, received an approvalGehua, Beijing Fastweb Network Technology Co., Ltd., or BJ Fastweb, and Guangdong Tianying Information Technology Co., Ltd., or GD Tianying, are entitled to enjoy a preferential tax rate of a six-year tax holiday effective from January 1, 2006, which allows it15% due to utilize a three-year 100% tax exemption followed by a three-year 50% reduced EIT rate.

In December 2008, 21Vianet Beijing also received an approvaltheir qualification as HNTE. The qualification as an HNTE is subject to annual administrative evaluation, a three-year review by the relevant authorities in China and becamea six-year reapplication.

21Vianet Beijing was qualified for an HNTE since 2008 and is eligible for a 15% preferential tax rate effective from 2008 to 2010.rate. In September 2011, 21VianetOctober 2014, 21Viaent Beijing renewed its HNTE status and became eligible forobtained a 15% preferential tax rate effective from 2011 to 2013. In accordance with the New EIT Law, in the event that any of the various provisions of the transitional preferential EIT policies, the New EIT Law and its implementing regulations overlap, an enterprise may choose the most favorable policy at its sole and absolute discretion. 21Vianet Beijing applied the tax holiday for the years endednew certificate, which will expire on December 31, 2010 and 2011 and enjoyed a preferential tax rate of 12.5%. For the years ended December 31, 2012 and 2013, 21Vianet Beijing applied the 15% preferential tax rate.2016.

In April 2011, 21Vianet (Xi’an) Information Outsourcing Industry Park Services Co., Ltd., or 21Vianet Xi’an, obtained a written approval from Shaanxi Tax Bureau for a preferential tax rate of 15%. The preferential tax rate is awarded to companies that have operations in certain industries and meet the criteria set forth in the Preferential Tax Policies for Development of the Western Regions. Such qualification for preferential tax rate needs to be assessed on an annual basis. In July 2012, Gehua received an approvalwas qualified as an HNTE and became eligible for a 15% preferential tax rate effective from 2012 to 2014, and thereafter for an additional three years thereafter if it is able to meet the technical and administrative requirements for HNTE in those three years.

In June 2009, BeijingBJ Fastweb Network Technology Co., Ltd., or Fastweb BJ, received an approvalwas qualified as an HNTE and became eligible for a 15% preferential tax rate effective from 2009 to 2011.2011, and thereafter for an additional three years if it is able to meet the HNTE technical and administrative requirements in those three years. After Fastweb BJ’sBJ Fastweb’s HNTE certificate expired onas of December 31, 2011, a renewed certificate was issued to BJ Fastweb BJ in May 2012, which has expired on December 31, 2014. BJ Fastweb is in the process of renewing the HNTE certificate and it is still eligible for a 15% preferential tax rate as long as the renewed certificate is issued before December 31, 2015.

In 2010, GD Tianying was qualified as an HNTE and became eligible for a 15% preferential tax rate effective from 2010 to 2012, and thereafter for an addition three years if it is able to meet the HNTE technical and administrative requirements in those three years. GD Tianying’s HNTE certificate expired as of December 31, 2012 and GD Tianying obtained a renewed certificate in October 2013, which will expire on December 31, 2014. The qualification as an HNTE is subject to annual administrative evaluation2015.

In 2000 and a three-year review by the relevant authorities in China. In 2013, Beijing iJoy Information2012, Sichuan Aipu Network Co., Ltd., or SC Aipu, and Yunnan Aipu Network Technology Co., Ltd., or BeijingYunnan Aipu, two companies within the Aipu Group, were qualified for a preferential tax rate of 15%.

In April 2011, 21Vianet (Xi’an) Information Outsourcing Industry Park Services Co., Ltd., or 21Vianet Xi’an was qualified for a preferential tax rate of 15%.The preferential tax rate is awarded for companies that have operations in certain industries and meet the criteria of the Preferential Tax Policies for Development of the Western Regions. The qualification will need to be assessed on an annual basis.

In 2013, BJ iJoy was qualified as a software enterprise which allows it to utilize a two-year 100% tax exemption for 2013 and 2014 followed by a three-year 50% reducedhalf-reduced EIT rate effective for the years from 20132015 to 2017. For the year ended December 31, 2013, Beijing iJoy enjoyed 100% tax exemption for its taxable income in 2013.

If 21Vianet Beijing, Gehua, BJ Fastweb and Fastweb BJGD Tianying fail to maintain or renew their HNTE status, or if 21Vianet Xi’an, isSC Aipu and Yunnan Aipu are not able to enjoy itstheir preferential tax treatment under Preferential Tax Policies for Development of the Western Regions, or if BeijingBJ iJoy fails to maintain or renew its software enterprise status, their applicable EIT rate may be increased to 25%, which could have a material adverse effect on our financial condition and results of operations.

The M&A Rules establish complex procedures for some acquisitions of Chinese companies by foreign investors, which could make it difficult for us to pursue growth through acquisitions in China.

The M&A Rules include provisionsand other recently adopted regulations and rules concerning mergers and acquisitions established additional procedures and requirements that purport to require approvalcould make merger and acquisition activities by foreign investors more time consuming and complex. In addition, the Implementing Rules Concerning Security Review on the Mergers and Acquisitions by Foreign Investors of Domestic Enterprises, issued by the Ministry of Commerce forMOC in August 2011, specify that mergers and acquisitions by offshore entities established or controlled by domestic companies, enterprises or natural persons of onshore entities that areforeign investors involved in “an industry related to such domestic companies, enterprises or natural persons,national security” are subject to strict review by the MOC, and prohibit offshore entities from using their foreign-invested subsidiariesany activities attempting to bypass such security review, including by structuring the transaction through a proxy or contractual control arrangement. We believe that our business is not in China,an industry related to national security, but we cannot preclude the possibility that the MOC or through “other means,”other government agencies may publish explanations contrary to circumventour understanding or broaden the scope of such requirement. As partsecurity reviews in the future, in which case our future acquisitions in the PRC, including those by way of our growth strategy, we obtained control over 21Vianet Technology in July 2003 by entering into contractual control arrangements with our variable interesttarget entities, and their shareholders. We obtained control over Beijing iJoymay be closely scrutinized or prohibited. Moreover, the Anti-Monopoly Law requires that the MOC be notified in April 2013 following completionadvance of our acquisitionany concentration of 100% equity interest in iJoy and with our contractual arrangements with Beijing iJoy. We did not seek the approval of the Ministry of Commerce for these transactions based on the legal advice we obtained from our PRC legal counsel in connection with those transactions. However, the M&A Rules also prohibit companies from using any “other means” to circumvent the approval requirement set forth therein and there is no clear interpretation as to what constitutes “other means” of circumvention of the requirement under the M&A Rules. The Ministry of Commerce and other applicable government authorities would therefore have broad discretion in determining whether an acquisition is in violation of the M&A Rules. If PRC regulatory authorities take a view that is contrary to ours, we could be subject to severe penalties. In addition, partundertaking if certain filing thresholds are triggered. Part of our growth strategy includes acquiring complementary businesses or assets.assets in China. Complying with the requirements of the M&A Rulelaws and regulations mentioned above and other PRC regulations to complete such transactions could be time-consuming, and any required approval processes, including obtaining approval from the Ministry of Commerce,MOC, may delay or inhibit the completion ofour ability to complete such transactions, which could affect our ability to expand our business or maintain our market share. If any of our acquisitions were subject to the M&A Rule and were found not to be in compliance with the requirements of the M&A Rule in the future, relevant PRC regulatory agencies may impose fines and penalties

on our operations in the PRC, limit our operating privileges

in the PRC, or take other actions that could have a material adverse effect on our business, financial condition, results of operations, reputation and prospects.

PRC regulation of loans and direct investment by offshore holding companies to PRC entities may delay or prevent us from using the proceeds from our overseas offerings to make loans or additional capital contributions to our PRC subsidiaries or consolidated affiliated entities, which could materially and adversely affect our liquidity and our ability to fund and expand our business.

In utilizing the proceeds we received from our overseas offerings or in other financing activities, as an offshore holding company, we may make loans to our PRC subsidiaries or our consolidated affiliated entities in the PRC, or we may make additional capital contributions to our PRC subsidiaries.subsidiaries or consolidated affiliated entities. Any loans to our PRC subsidiaries or our consolidated affiliated entities in the PRC are subject to PRC regulations. For example, loans by us to our PRC subsidiaries, which are foreign-invested enterprises,FIEs, to finance their activities cannot exceed statutory limits and must be registered with the State Administration of Foreign Exchange, or SAFE.

We may also decide to finance our operations in China by means of capital contributions. These capital contributions must be approved by the Ministry of CommerceMOC or its local counterpart. We cannot assure you that we will be able to obtain these government approvals on a timely basis, if at all, with respect to future capital contributions by us to our subsidiaries. If we fail to receive such approvals, our ability to use the proceeds from our overseas offerings and to capitalize our PRC operations may be negatively affected, which could adversely affect our liquidity and our ability to fund and expand our business.

Governmental control of currency conversion may limit our ability to receive and utilize our revenues effectively.

We earn substantially all of our revenues and incur most of our expenses in Renminbi. Under PRC laws, theRenminbi; however, Renminbi is currentlynot freely convertible underat present.

The PRC government continues to regulate conversion between Renminbi and foreign currencies, despite the “current account,” which includes dividends,significant reduction in its control in recent years over trade transactions involving import and service relatedexport of goods and services as well as other frequent routine foreign exchange transactions. These transactions but not underare known as current account items. However, remittance of Renminbi by foreign investors into the “capitalPRC for the purposes of capital account” which includes foreign direct investment items, such as capital contributions, is generally permitted upon obtaining specific approvals from, or completing specific registrations or filings with, the relevant authorities on a case-by-case basis and loans, withoutis subject to a strict monitoring system. Regulations in the prior approvalPRC on the remittance of Renminbi into the SAFE.PRC for settlement of capital account items are developing gradually. Currently, our PRC subsidiaries may purchase foreign currencies for settlement of current account transactions, including payments of dividends to us, without the approval of the SAFE. However, foreign exchange transactions by our PRC subsidiaries under the capital account continue to be subject to significant foreign exchange controls and require the approval of or need to register with PRC governmental authorities, including the SAFE. In particular, if our PRC subsidiaries borrow foreign currency loans from us or other foreign lenders, these loans must first be registered with the SAFE. If any of our PRC subsidiaries, which are wholly foreign-owned enterprises, borrows foreign currency, the accumulative amount of its foreign currency loans may not exceed the difference between the total investment and the registered capital of that PRC subsidiary. If we finance our PRC subsidiaries by means of additional capital contributions, these capital contributions must be approved by certain government authorities, including the National Development and Reform Commission, the Ministry of CommerceMOC or their respective local counterparts. Any existing and future restrictions on currency exchange may affect the ability of our PRC subsidiaries or affiliated entities to obtain foreign currencies, limit our ability to meet our foreign currency obligations or otherwise materially and adversely affect our business.

Fluctuation in exchange rates could have a material adverse effect on our results of operations and the value of your investment.

The conversion of Renminbi into foreign currencies, including U.S. dollars, is based on rates set by the People’s Bank of China. The PRC government allowed the Renminbi to appreciate by more than 20% against the U.S. dollar between July 2005 and July 2008. Between July 2008 and June 2010, this appreciation was halted and the exchange rate between the Renminbi and the U.S. dollar remained within a narrow band. As a consequence, the Renminbi fluctuated significantly during that period against other freely traded currencies, in tandem with the U.S. dollar. Since June 2010, the PRC government has allowed the Renminbi to appreciate slowly against the U.S. dollar again, though there have been periods recently when the U.S. dollar has appreciated against the Renminbi. The People’s Bank of China decided to further adjust the Renminbi exchange rate regime in March 2014 to enhance the flexibility of the Renminbi exchange rate by enlarging the floating band of the Renminbi’s trading prices against the U.S. dollar in the interbank spot foreign exchange market from the current 1.0% to

2.0%. It is difficult to predict how market forces or PRC or U.S. government policy may impact the exchange rate between the Renminbi and the U.S. dollar in the future.

There remains significant international pressure on the Chinese government to adopt a substantial liberalization of its currency policy, which could result in further appreciation in the value of the Renminbi against the U.S. dollar. To the extent that we need to convert U.S. dollars into Renminbi for capital expenditures and working capital and other business purposes, appreciation of the Renminbi against the U.S. dollar would have an adverse effect on the Renminbi amount we would receive from the conversion. Conversely, if we decide to convert Renminbi into U.S. dollars for the purpose of making payments for dividends on our ordinary shares or ADSs, strategic acquisitions or investments or other business purposes, appreciation of the U.S. dollar against the Renminbi would have a negative effect on the U.S. dollar amount available to us.

PRC regulations relating to the establishment of offshore special purpose companiesvehicles by PRC residents may subject our PRC resident beneficial owners to personal liability and limit our ability to acquire PRC companies, to inject capital into our PRC subsidiaries, limit our PRC subsidiaries’ ability to distribute profits to us, or otherwise materially and adversely affect us.

In October 2005, SAFE issued the Circular on the Relevant Issues in the Foreign Exchange Control over Financing and Return Investment Through Special Purpose Companies by Residents Inside China, or Circular 75.75, which is now replaced by the Circular on Relevant Issues Concerning Foreign Exchange Control on Domestic Residents’ Offshore Investment and Financing and Roundtrip Investment through Special Purpose Vehicles, or Circular 37, issued by SAFE on July 4, 2014. According to Circular 7537, PRC residents are required to register with local SAFE branches in connection with their direct establishment or indirect control of an offshore entity for the purposes of overseas investment and financing, with such PRC residents’ legally owned assets or equity interests in domestic enterprises or offshore assets or interests, referred to in Circular 37 as a “special purpose vehicle.” The term “control” under Circular 37 is broadly defined as the relevant SAFE regulations, prioroperation rights, beneficiary rights or decision-making rights acquired by the PRC residents in the offshore special purpose vehicles or PRC companies by such means as acquisition, trust, proxy, voting rights, repurchase, convertible bonds or other arrangements. Circular 37 further requires amendment to the registration in the event of any changes with respect to the basic information of the special purpose vehicle, such as changes in a PRC resident individual shareholder, name or operation period; or any significant changes with respect to the special purpose vehicle, such as increase or decrease of capital contributed by PRC individuals, share transfer or exchange, merger, division or other material event. If the shareholders of the offshore holding company who are PRC residents do not complete their registration with the local SAFE branch is required for PRC residents to establish or to control an offshore company for the purposes of financing that offshore company with assets or equity interests in an onshore enterprise located in the PRC. An amendment to registration or filing with the local SAFE branch by such PRC resident is also required for the injection of equity interests or assets of an onshore enterprise in the offshore company or overseas funds raised by such offshore company or another material change involving a change in the capital of the offshore company.

Moreover, Circular 75 applies retroactively. As a result, PRC residents who have established or acquired control of offshore companies that have made onshore investments inbranches, the PRC in the past are required to complete the relevant registration with the local SAFE branch. Failure to comply with the registration procedures set forth in Circular 75subsidiaries may result in restrictions on the foreign exchange activities of the relevant foreign invested enterprises, including the payment of dividendsbe prohibited from distributing their profits and other distributions, such as proceeds from any reduction in capital, share transfer or liquidation to itsthe offshore parent or affiliatecompany, and the offshore company may be restricted in its ability to contribute additional capital inflow fromto its PRC subsidiaries. Moreover, failure to comply with SAFE registration and amendment requirements described above could result in liability under PRC law for evasion of applicable foreign exchange restrictions. On February 13, 2015, SAFE promulgated a Notice on Further Simplifying and Improving Foreign Exchange

Administration Policy on Direct Investment, or SAFE Notice 13, which will take effect on June 1, 2015. SAFE Notice 13 has delegated to the offshore parent, and may also subject relevantqualified banks the authority to register all PRC residents’ investment in “special purpose vehicle” pursuant to the Circular 37, except that those PRC residents to penalties under PRC foreign exchange administration regulations.

According to Circular 75 and the relevant SAFE regulations, any PRC citizen, resident, or entity which is a direct or indirect shareholder of an offshore entity is required to update any previously filed registration with the local branch of SAFE to reflect any material change in such offshore entity. Moreover, any offshore entity which failswho have failed to comply with Circular 75 may remedy by making37 will remain to fall into the jurisdiction of the local SAFE branches and must make their supplementary registration application with the local branch of SAFE after fulfillment of the administrative penalties imposed by the relevant SAFE branch.branches.

Our current PRC resident beneficial owners, including our co-founders Sheng Chen and Jun Zhang, are stillhave filed the foreign exchange registration in connection with their respective overseas shareholding in our Company in accordance with the process of filing the necessary registrations as required under Circular 75. Registration with SAFE may take quite a long time and is subject to SAFE’s discretion to approve such registration.37 on June 10, 2014. We cannot assure you when our co-founders can successfully complete their registrations. We have also requested other PRC residents holdingwho we know hold direct or indirect interest in our company to our knowledge to make the necessary applications, filings and amendments as required under Circular 7537 and the relevant SAFE regulations.other related rules. We attempt to comply, and attempt to ensure that these PRC residents holding direct or indirect interest in our company comply, with the relevant requirements, and those persons holding direct or indirect interests in our securities whose identities and addresses we know and who are subject to Circular 7537 and the relevant SAFE regulations have conducted the registration procedures prescribed by Circular 7537 and will update such registration. However, we may not be informed of the identities of all the PRC residents holding direct or indirect interest in our company, and we cannot provide any assurances that these PRC residents will comply with our request to make or obtain any applicable registrations or comply with other requirements required by Circular 7537 or the relevant SAFE regulations. The failure or inability of PRC residents, including our co-founders, to make any required registrations or comply with other requirements under Circular 7537 and the relevant SAFE regulations may subject

such PRC residents or our PRC subsidiaries to fines and legal sanctions and may also limit our ability to contribute additional capital into or provide loans to our PRC subsidiaries and our consolidated affiliated entities, limit our PRC subsidiaries’ ability to pay dividends or otherwise distribute profits to us, or otherwise materially and adversely affect us.

Failure to comply with the registration requirements for employee share option plans may subject our equity incentive plan participants who are PRC residents or us to fines and other legal or administrative sanctions.

Since 2007, SAFE has implemented rules requiring PRC residents who participate in employee stock option plans of overseas publicly listed companies to register with SAFE or its local office and complete certain other procedures. Effective on February 15, 2012, SAFE promulgated the Circular on the Relevant Issues Concerning Foreign Exchange Administration for Domestic Individuals Participating in an Employees Share Incentive Plan of an Overseas-Listed Company, or CircularSAFE Notice 7. Under CircularSAFE Notice 7, PRC residents who participate in a share incentive plan of an overseas publicly listed company are required to register with SAFE and complete certain other procedures. PRC residents include directors, supervisors, management and employees of PRC domestic companies specified in the Administrative Regulations of the People’s Republic of China on Foreign Exchange, regardless of nationality. CircularSAFE Notice 7 further requires that an agent should also be designated to handle matters in connection with the exercise or sale of share options granted under the share incentive plan to participants. We and the PRC residents to whom we have granted stock options are subject to CircularSAFE Notice 7. If we or our PRC optionees fail to comply with these regulations, we or our PRC optionees may be subject to fines and other legal or administrative sanctions.

Risks Related to our ADSs

The market price of our ADSs has fluctuated and may continue to be volatile.

The trading prices of our ADSs are likely to be volatile and could fluctuate widely due to factors beyond our control. This may happen because of broad market and industry factors, such as the performance and fluctuation in the market prices or the underperformance or declining financial results of other companies based in China that have listed their securities in the United States in recent years. The securities of some of these companies have experienced significant volatility since their initial public offerings, including, in some cases, substantial price declines in the trading prices of their securities. The trading performances of other Chinese companies’

securities after their offerings may affect the attitudes of investors toward Chinese companies listed in the United States, which consequently may impact the trading performance of our ADSs, regardless of our actual operating performance. The recent ongoing administrative proceedings brought by SEC against five accounting firms in China, alleging that they refused to hand over documents to the SEC for ongoing investigations into certain China-based companies, occurs at a time when accounting scandals have eroded investor appetite for China-based companies. Any other negative news or perceptions about inadequate corporate governance practices or fraudulent accounting, corporate structure or matters of the Chinese companies may also negatively affect the attitudes of investors towards Chinese companies in general, including us, regardless of whether we have conducted any inappropriate activities. In addition, securities markets may from time to time experience significant price and volume fluctuations that are not related to our operating performance, which may have a material and adverse effect on the market price of our ADSs.

In addition, the market price for our ADSs has fluctuated since we first listed our ADSs on the NASDAQ Global Select Market on April 21, 2011, until April 8, 2014,9, 2015, the trading prices of our ADSs have ranged from US$8.31 to US$32.1932.34 per ADS, and the last reported closing price on April 8, 20149, 2015 was US$25.0719.90 per ADS. The market price for our ADSs may be highly volatile and subject to wide fluctuations in response to factors including the following:

Our dual-class voting structure will limit your ability to influence corporate matters and could discourage others from pursuing any change of control transactions that holders of our Class A ordinary shares and ADSs may view as beneficial.

We have a dual-class voting structure such that our ordinary shares consist of Class A ordinary shares and Class B ordinary shares. In respect of matters requiring the votes of shareholders, holders of Class A ordinary shares are entitled to one vote per share, while holders of Class B ordinary shares are entitled to ten votes per share. Each Class B ordinary share is convertible into one Class A ordinary share at any time by the holder thereof, while Class A ordinary shares are not convertible into Class B ordinary shares or preferred shares under

any circumstances. Upon any transfer of Class B ordinary shares by a holder thereof to any person or entity which is not an affiliate of such holder, such Class B ordinary shares shall be automatically and immediately converted into the equal number of Class A ordinary shares. Due to the disparate voting powers attached to these two classes, holders of our Class B ordinary shares have significant voting power over matters requiring shareholder approval. This concentrated control will limit your ability to influence corporate matters and could discourage others from pursuing any potential merger, takeover or other change of control transactions that holders of Class A ordinary shares and ADSs may view as beneficial.

Future sales of a substantial number of our ADSs in the public market, or the perception that these sales could occur, could cause the price of our ADSs to decline.

In the future, we may sell additional ADSs to raise capital, and our existing shareholders could sell substantial amounts of ADSs, including those issued upon the exercise of outstanding options, in the public market. We cannot predict the size of any future issuance of ADSs or the effect that future sales of our ADSs would have on the market price of our ADSs. Any future sales of a substantial number of our ADSs in the public market, or the perception that these sales could occur, could cause the trading price of our ADSs to decline and impair our ability to raise capital through the sale of additional equity securities.

You may not have the same voting rights as the holders of our ordinary shares and may not receive voting materials in time to be able to exercise your right to vote.

Except as described in this annual report and in the deposit agreement, holders of our ADSs are not able to exercise voting rights attaching to the Class A ordinary shares evidenced by our ADSs on an individual basis. Holders of our ADSs will appoint the depositary or its nominee as their representative to exercise the voting rights attaching to the Class A ordinary shares represented by the ADSs. Otherwise, you will not be able to exercise your right to vote unless you withdraw the Class A ordinary shares represented by the ADSs. However, you may not know of the meeting sufficiently in advance to withdraw the ordinary shares. If we ask for instructions from ADS holders, the depositary will notify you of the upcoming vote and arrange to deliver our

voting materials to you. We cannot assure you that you will receive voting materials in time to instruct the depositary to vote, and it is possible that you, including persons who hold their ADSs through brokers, dealers or other third parties, will not have the opportunity to exercise a right to vote. The deposit agreement provides that if the depositary does not timely receive valid voting instructions from the ADS holders, then the depositary will, with certain limited exceptions, give a discretionary proxy to a person designated by us to vote such shares.

We are exempt from certain corporate governance requirements of NASDAQ and we intend to rely on certain exemptions.

Certain corporate governance practices in the Cayman Islands, which is our home country, are considerably different than the standards applied to U.S. domestic issuers. NASDAQ Marketplace Rules provide that foreign private issuers are exempt from certain corporate governance requirements of NASDAQ and may follow their home country practices, subject to certain exceptions and requirements to the extent that such exemptions would be contrary to U.S. federal securities laws and regulations. We currently follow our home country practice thatthat: (i) does not require us to solicit proxy and hold meetings of our shareholders every year, as well as seeking shareholders’ approval(ii) does not restrict a company’s transactions with directors, requiring only that directors exercise a duty of care and owe a fiduciary duty to the companies for amending our share incentive plan. In the future, we may rely on other exemptions provided by NASDAQ, including the exemption thatwhich they serve, (iii) does not require us to obtain shareholder approval for issuing additional securities exceeding 20% of our outstanding ordinary shares.shares, and (iv) does not require us to seek shareholders’ approval for amending our share incentive plan. As a result, our investors may not be provided with the benefits of certain corporate governance requirements of NASDAQ.

We may be classified as a passive foreign investment company for United States federal income tax purposes, which could result in adverse U.S. federal income tax consequences to U.S. holders of our ADSs or Class A ordinary shares.

Based on the market price of our ADSs and Class A ordinary shares, the value of our assets, and the composition of our assets and income, we believe that we were not a passive foreign investment company (a “PFIC”) for United States federal income tax purposes for our taxable year ended December 31, 20132014 and we do not expect to be a PFIC for the current year or for the foreseeable future. Nevertheless, the application of the PFIC rules is subject to ambiguity in several respects and, in addition, we must make a separate determination each year as to whether we are a PFIC (after the close of each taxable year). Accordingly, we cannot assure you that we will not be a PFIC for our current taxable year or for any future taxable year.

A non-U.S. corporation, such as our company, will be considered a PFIC for United States federal income tax purposes for any taxable year if either (i) 75% or more of its gross income for such year consists of certain types of “passive” income or (ii) 50% or more of the value of its assets (determined on the basis of a quarterly average) during such year produce or are held for the production of passive income, or the asset test. While we do not anticipate being a PFIC, changes in the nature of our income or assets or the value of our assets may cause us to become a PFIC for the current or any subsequent taxable year. Under circumstances where revenues from activities that produce passive income significantly increase relative to our revenues from activities that produce non-passive income or where we determine not to deploy significant amounts of cash for active purposes, our risk of becoming classified as a PFIC may substantially increase.

Although the law in this regard is not entirely clear, we treat our variable interest entities as being owned by us for United States federal income tax purposes because we control their management decisions and we are entitled to substantially all of their economic benefits and, as a result, we consolidate their results of operations in our consolidated U.S. GAAP financial statements. If it were determined, however, that we are not the owner of our variable interest entities for United States federal income tax purposes, we would likely be treated as a PFIC for our taxable year ended December 31, 20132014 and for subsequent taxable years.

If we were to be or become a PFIC, a U.S. Holder (as defined in “Item 10.E. Additional Information—Taxation—Certain United States Federal Income Tax Considerations—General”) may incur significantly increased United States income tax on gain recognized on the sale or other disposition of the ADSs or Class A

ordinary shares and on the receipt of distributions on the ADSs or Class A ordinary shares to the extent such gain or distribution is treated as an “excess distribution” under the United States federal income tax rules. For more information, see “Item 10.E. Additional Information—Taxation—Certain United States Federal Income Tax Considerations—Passive Foreign Investment Company Considerations.”

You may not be able to participate in rights offerings, may experience dilution of your holdings and you may not receive certain distributions on Class A ordinary shares if it is impractical to make them available to you.

We may from time to time distribute rights to our shareholders, including rights to acquire our securities. Under the deposit agreement for the ADSs, the depositary will not offer those rights to ADS holders unless both the rights and the underlying securities to be distributed to ADS holders are either registered under the Securities Act or exempt from registration under the Securities Act with respect to all holders of ADSs. We are under no obligation to file a registration statement with respect to any such rights or underlying securities or to endeavor to cause such a registration statement to be declared effective. In addition, we may not be able to take advantage of any exemptions from registration under the Securities Act. Accordingly, holders of our ADSs may be unable to participate in our rights offerings and may experience dilution in their holdings as a result.

In addition, the depositary of our ADSs has agreed to pay to you the cash dividends or other distributions it or the custodian receives on our ordinary shares or other deposited securities after deducting its fees and expenses. You will receive these distributions in proportion to the number of Class A ordinary shares your ADSs

represent. However, the depositary may, at its discretion, decide that it is unlawful or impractical to make a distribution available to any holders of ADSs. For example, the depositary may determine that it is not practicable to distribute certain property through the mail, or that the value of certain distributions may be less than the cost of mailing them. In these cases, the depositary may decide not to distribute such property and you will not receive such distribution.

You may be subject to limitations on transfer of your ADSs.

Your ADSs represented by the ADRs are transferable on the books of the depositary. However, the depositary may close its transfer books at any time or from time to time when it deems expedient in connection with the performance of its duties. In addition, the depositary may refuse to deliver, transfer or register transfers of ADSs generally when our books or the books of the depositary are closed, or at any time if we or the depositary deem it advisable to do so because of any requirement of law or of any government or governmental body, or under any provision of the deposit agreement, or for any other reason.

You may face difficulties in protecting your interests, and your ability to protect your rights through the U.S. federal courts may be limited, because we are incorporated under Cayman Islands law, conduct all of our operations in China and a majority of our officers and directors reside outside the United States.

We are incorporated in the Cayman Islands and substantially all of our assets are located outside of the United States. We conduct all of our operations in China through our wholly-owned subsidiarysubsidiaries in China. The majority of our officers and directors reside outside the United States and a substantial portion of the assets of those persons are located outside of the United States. As a result, it may be difficult for you to bring an action against us or against these individuals in the Cayman Islands or in China in the event that you believe that your rights have been infringed under the securities laws or otherwise. Even if you are successful in bringing an action of this kind, the laws of the Cayman Islands and of China may render you unable to enforce a judgment against our assets or the assets of our directors and officers. In addition, there is uncertainty as to whether the courts of the Cayman Islands or the PRC would recognize or enforce judgments of U.S. courts against us or our directors and officers predicated upon the civil liability provisions of the securities laws of the United States or any state, and it is uncertain whether such Cayman Islands or PRC courts would be competent to hear original actions brought in the Cayman Islands or the PRC against us or our directors and officers predicated upon the securities laws of the United States or any state, on the ground that such provisions are penal in nature.

Our corporate affairs are governed by our memorandum and articles of association and by the Companies Law (as amended) and common law of the Cayman Islands. The rights of shareholders to take legal action against our directors and us, actions by minority shareholders and the fiduciary responsibilities of our directors to us under Cayman Islands law are to a large extent governed by the common law of the Cayman Islands. The common law of the Cayman Islands is derived in part from comparatively limited judicial precedent in the Cayman Islands as well as from English common law, which has persuasive, but not binding, authority on a court in the Cayman Islands. The rights of our shareholders and the fiduciary responsibilities of our directors under Cayman Islands law are not as clearly established as they would be under statutes or judicial precedents in the United States. In particular, the Cayman Islands has a less developed body of securities laws as compared to the United States, and provides significantly less protection to investors. In addition, Cayman Islands companies may not have standing to initiate a shareholder derivative action before the federal courts of the United States.

As a result of all of the above, our public shareholders may have more difficulty in protecting their interests through actions against our management, directors or major shareholders than they would as shareholders of a public company of the United States.

Our memorandum and articles of association contain anti-takeover provisions that could adversely affect the rights of holders of our ordinary shares and ADSs.

Our memorandum and articles of association contain certain provisions that could limit the ability of others to acquire control of our company, including our dual-class voting structure, and a provision that grants authority to our board of directors to establish from time to time one or more series of preferred shares without action by our shareholders and to determine, with respect to any series of preferred shares, the terms and rights of that series. These provisions could have the effect of depriving our shareholders of the opportunity to sell their shares at a premium over the prevailing market price by discouraging third parties from seeking to obtain control of our company in a tender offer or similar transactions.

We have incurred increased costs as a result of being a public company.

As a public company, we have incurred significant accounting, legal and other expenses that we did not incur as a private company. The Sarbanes-Oxley Act, as well as new rules subsequently implemented by the SEC and the NASDAQ Global Select Market, have detailed requirements concerning corporate governance practices of public companies including Section 404 of the Sarbanes-Oxley Act relating to internal controls over financial reporting. These new rules and regulations have increased our director and officer liability insurance, accounting, legal and financial reporting compliance costs and have made certain corporate activities more time-consuming and costly. Therefore, we have incurred additional costs associated with our public company reporting requirements, and we cannot predict or estimate the amount of additional costs we may further incur or the timing of such costs.

If securities or industry analysts do not actively follow our business, or if they publish unfavorable research about our business, our ADS price and trading volume could decline.

The trading market for our ADS depends in part on the research and reports that securities or industry analysts publish about us or our business. If one or more of the analysts who covers us downgrades our ADSs or publishes unfavorable research about our business, our ADS price would likely decline. If one or more of these analysts ceases coverage of our company or fails to publish reports on us regularly, demand for our ADSs could decrease, which could cause our ADS price and trading volume to decline.

A.History and Development of the Company

We commenced our operations in 1999, and through a series of corporate restructurings, set up a holding company, AsiaCloud Inc., or AsiaCloud, in October 2009 under the laws of the Cayman Islands. AsiaCloud was

formerly a wholly-owned subsidiary of aBitCool Inc., or aBitCool, a company incorporated under the laws of the Cayman Islands. In October 2010, AsiaCloud effected a restructuring whereby AsiaCloud repurchased all its outstanding shares held by aBitCool and issued ordinary shares and preferred shares to the same shareholders of aBitCool. In connection with the restructuring, AsiaCloud subsequently changed its name to 21Vianet Group, Inc.

Due to certain restrictions under the PRC laws on foreign ownership of entities engaged in data center and telecommunications value-added services, we conduct our operations in China through contractual arrangements among us, our wholly-owned PRC subsidiaries, our variable interest entities and their shareholders. As a result of these contractual arrangements, we control our variable interest entities and have consolidated the financial information of our consolidated affiliated entities in our consolidated financial statements in accordance with U.S. GAAP. We ownown: (i) 100% of the equity interests in 21Vianet China through our subsidiary, 21ViaNet Group Limited, or 21Vianet HK, which was incorporated in Hong Kong in May 2007. We also own2007; (ii) 100% of the equity interests of SuzhouSZ Zhuoaiyi following completion of our acquisition of 100% equity interests in iJoy in April 2013.2013; and (iii) 100% of the equity interests of aBitCool BJ through our subsidiary, aBitCool DG, which was incorporated in June 2014.

On April 21, 2011, our ADSs began trading on the NASDAQ Global Select Market under the ticker symbol “VNET.” We issued and sold a total of 14,950,000 ADSs, representing 89,700,000 Class A ordinary shares, at an initial offering price of US$15.00 per ADS.

As part of our growth strategy, we have acquired companies that are complementary to our business, as well as made alternative investments and entered into strategic partnerships or alliances as we see fit. For example:

Our principal executive offices are located at M5, 1 Jiuxianqiao East Road, Chaoyang District, Beijing, 100016, the People’s Republic of China. Our telephone number at this address is +8610 8456 2121.+86 (10) 8456-2121. Our registered office in the Cayman Islands is located at the offices of Maples Corporate Services Limited, PO Box 309, Ugland House, Grand Cayman, KY1-1104, Cayman Islands. Our agent for service of process in the U.S. is Law Debenture Corporate Services Inc., located at 400 Madison Avenue, 4th Floor, New York, New York 10017.

See Item 4.C, “Organizational Structure” for a diagram illustrating our corporate structure as of the dated of this annual report.

B.Business Overview

Overview

We are the largesta leading carrier-neutral internet data center services provider in China as measured by revenues in 2012, according to data released by IDC, an independent third-party research firm.China. We host our customers’ servers and networking equipment and provide interconnectivity to improve the performance, availability and security of their internet infrastructure. We also provide managed network services to enable customers to deliver data across the internet in a faster and more reliable manner through our extensive data transmission network and our proprietary smart routing technology. Furthermore, we provide complementary internet infrastructure services, such as CDN services, VPN services and last-mile wired broadband services to improve the security, speed and quality of data transmission in China. We started offering public cloud services in 2013 and private cloud and hybrid services in 2014. We believe that the scale of our data center and networking assets as well as our carrier-neutrality position us well to capture opportunities and become a leader in the rapidly emerging market for cloud computing infrastructure services in China.

Our infrastructure consists of our high-quality data centers and an extensive data transmission network. We operate 1216 self-built data centers and 6973 partnered data centers located in 43over 30 cities, throughout China, including substantially all of China’s major internet hubs with over 14,00021,522 cabinets under management that house over 76,00097,101 servers as of December 31, 2013.2014. We adopt a distributed deployment method when choosing locations for our partnered data centers based on the specific requests of our customers, demands in different cities and our strategy for POP establishment; therefore, the locations and number of our partnered data centers are subject to change from to time. Our data transmission network includes over 500 points of presence, or615 POPs, which are access points from one place to the rest of the internet. Most of our data centers and all of our POPs are connected by our private optical fibers network across China.

As a carrier-neutral internet infrastructure services provider, our infrastructure is interconnected with the networks operated by all China’s telecommunications carriers, major non-carriers and local internet service providers. The interconnectivity enables each of our data centers to function as a network access point for our customer’s data traffic. In addition, we believe that our proprietary smart routing technology allows us to automatically select an optimized route to direct our customers’ data traffic to ensure fast and reliable data transmission. We believe this advanced interconnectivity within and beyond our network distinguishes ourselves from our competitors and provides an effective solution to address our customers’ needs that arise from inadequate public internet infrastructure and network interconnectivity in China. As a result, businesses are increasingly relying upon internet infrastructure services providers and in particular, carrier-neutral internet infrastructure services providers, to enhance and optimize key elements of their IT and network infrastructure. Furthermore, we provide content delivery networkCDN services, VPN services, last-mile wired broadband services, public cloud services and will provide private and hybrid cloud services, in the near future, which strengthens our capability to provide quality services and meet customer demand in our ecosystem.

We serve a diversified and loyal base of customers, spanning many different industries and ranging from internet companies to government entities, from blue-chip enterprises to small- to mid-sized enterprises. As of December 31, 2013,2014, we had 2,046had: (i) over 4,000 enterprise customers for our hosting services, including many leading Chineseover 2,000 enterprise customers for VPN services across China, Taiwan, Hong Kong, Singapore and global companies operating in China.Vietnam, brought by Dermot Entities; (ii) over one million individual househeld customers for last-mile wired broadband services, brought by Aipu Group; and (iii) more than 55,000 signed customers for the Windows Azure and Office 365 services. Our average monthly churn rate as measured by monthly recurring revenues was approximately 0.9% and 1.7% in 2012 and 2013. Our average monthly hosting churn rate, based on our core internet data center (IDC) business, was 0.6% in 2014. Our average monthly recurring revenue from our top 20 customers in 2013 has increased from RMB42.6RMB45.5 million in December 20122013 to RMB45.5RMB57.1 million (US$7.59.2 million) in December 2013.2014.

We generate revenues from providing hosting and related services and managed network services. Our net revenues increased from RMB1,020.9 million in 2011 to RMB1,524.2 million in 2012 and to RMB1,966.7 million in 2013 and to RMB2,876.4 million (US$324.9463.6 million) in 2013,2014, representing a CAGR of 38.8%37.4% from 20112012 to 2013.2014. The total number of

cabinets under our management increased from 7,816 as of December 31, 2011 to 11,917 as of December 31, 2012 and to 14,041 as of December 31, 2013.2013 and to 21,522 as of December 31, 2014. Our average monthly recurring revenues increased from RMB82.0 million in 2011 to RMB125.2 million in 2012 and to RMB146.6 million in 2013 and to RMB208.4 million (US$24.233.6 million) in 2013. We recorded a net profit of RMB45.9 million in 2011, which reflected share-based compensation expenses of RMB42.0 million.2014. Our net profit was RMB57.7 million in 2012, which reflected share-based compensation expenses of RMB67.6 million. We recorded a net loss of RMB47.0 million and RMB328.5 million (US$7.852.9 million) in 2013 and 2014, respectively, which reflected share-based compensation expenses of RMB67.8 million and RMB233.7 million (US$11.237.7 million)., respectively. Our results of operations also reflect the effects of our acquisitions during the respective periods.

Our Service Offerings

We primarily generate revenues from providing hosting and related services and managed network services. We provide hosting and related services to house servers and networking equipment in our data centers and connect them through our data transmission network, and offer other hosting related value-added services. We also provide, as part of our hosting and related services business, cloud services, CDN services and VPN services. Our managed network services allow our customers to transmit data across the internet in a faster and more reliable manner by leveraging our smart routing optimization technology through our hosting area network and data transmission network. WeOur managed network services also provide, as part of our hosting and related services business, cloud services and content delivery networkinclude last-mile wired broadband services.

Hosting and Related Services

Our hosting and related services including the following:

Our data centers host the servers of our customers and meet their needs to deploy computing, network, storage and IT infrastructure. Our hosting and related services are scalable, allowing our customers to purchase space and upgrade connectivity and services as their requirements evolve. In addition, our customers benefit from our data centers’ wide range of physical security features, including sensitive smoke detection systems, fire suppression systems, secured access, around-the-clock video camera surveillance and security breach alarms. Our data centers are fully-redundant and feature resilient power supplies, energy efficient design, connection with multiple network providers and 24/7 on-site support provided by our skilled engineers. As a result, we are able to guarantee 99.99% uptime for power in our service level agreements.

We believe another main reason customers choose our services is our access to multiple carriers and service providers and the availability of multiple-provider bandwidth. By securing multiple suppliers for connectivity and using redundant hardware, we are able to guarantee 99.9% internet connectivity uptime.

Managed Hosting Services

Our managed hosting services allow customers to lease partial or entire cabinet for their servers. Our customers have full control over their server(s) housed in our data centers. Depending on customer needs, we provide different levels of tailored server administration services, including operating system support and assistance with updates, server monitoring, server backup and restoration, server security evaluation, firewall services, and disaster recovery. Our customers’ servers are housed in our data centers providing redundant power sources and heating, ventilating and air conditioning systems. Managed hosting service relieves customers from the daily pressures of IT infrastructure maintenance so that they can focus on their core businesses.

Customers have the option to either place their servers and equipment in standard cabinets dedicated for their private use, or in cabinets shared with other customers. They can customize their cabinet space for their servers, network connections and equipment. Customers can elect to buy the hardware that they place within their cabinets from their chosen suppliers. In addition, customers can also lease power-based space, sometimes in a cage, where they can place their own cabinets in our data centers.

Interconnectivity Services

Our interconnectivity services connect our data centers with China’s internet backbones and other networks in the following ways: