Exhibit 5.1

Our ref LWP/726901-000001/13480238v3

OneSmart International Education Group Limited

165 West Guangfu Road, Putuo District

Shanghai 200063

People’s Republic of China

31 October 2018

Dear Sirs

OneSmart International Education Group Limited (the “Company”)

We have acted as Cayman Islands legal counsel to the Company in connection with a registration statement on Form S-8 to be filed with the Securities and Exchange Commission (the “Commission”) on 31 October 2018 (the “Registration Statement”) relating to the registration under the United States Securities Act of 1933, as amended, (the “Securities Act”) of 466,986,590 class A ordinary shares, par value US$0.000001 per share (the “Shares”), issuable by the Company pursuant to the Company’s Amended and Restated 2015 Share Incentive Plan (the “Plan”).

For the purposes of giving this opinion, we have examined copies of the Registration Statement and the Plan. We have also reviewed copies of the fifth amended and restated memorandum and articles of association of the Company adopted by a special resolution passed on 2 March 2018 and effective immediately prior to the completion of the Company’s initial public offering of the Company’s American Depositary Shares representing its Class A Ordinary Shares (the “Memorandum and Articles”) and the minutes (the “Minutes”) of the meeting of the board of directors of the Company held on 5 February 2018 (the “Meeting”).

Based upon, and subject to, the assumptions and qualifications set out below, and having regard to such legal considerations as we deem relevant, we are of the opinion that:

1. The Shares to be issued by the Company and registered under the Registration Statement have been duly and validly authorized.

2. When issued and paid for in accordance with the terms of the Plan and in accordance with the Minutes, and when appropriate entries are made in the register of members (shareholders) of the Company, the Shares will be validly issued, fully paid and non-assessable.

In this opinion letter, the phrase “non-assessable” means, with respect to the issuance of the Shares, that a shareholder shall not, in respect of the relevant Shares, have any obligation to make further contributions to the Company’s assets (except in exceptional circumstances, such as involving fraud, the establishment of an agency relationship or an illegal or improper purpose or other circumstances in which a court may be prepared to pierce or lift the corporate veil).

These opinions are subject to the qualification that under the Companies Law (2018 Revision) of the Cayman Islands, the register of members of a Cayman Islands company is by statute regarded as prima facie evidence of any matters which the Companies Law (2018 Revision) directs or authorises to be inserted therein. A third party interest in the shares in question would not appear. An entry in the register of members may yield to a court order for rectification (for example, in the event of fraud or manifest error).

These opinions are given only as to, and based on, circumstances and matters of fact existing and known to us on the date of this opinion letter. These opinions only relate to the laws of the Cayman Islands which are in force on the date of this opinion letter. We express no opinion as to the meaning, validity or effect of any references to foreign (i.e. non-Cayman Islands) statutes, rules, regulations, codes, judicial authority or any other promulgations.

We have also relied upon the assumptions, which we have not independently verified, that (a) all signatures, initials and seals are genuine, (b) copies of documents, conformed copies or drafts of documents provided to us are true and complete copies of, or in the final forms of, the originals, (c) there is nothing contained in the minute book or corporate records of the Company (which we have not inspected) which would or might affect the opinions set out above, (d) the Minutes are a true and correct record of the proceedings of the Meeting, which was duly convened and held, and at which a quorum was present throughout, in each case, in the manner prescribed in the Memorandum and Articles, (e) the resolutions set out in the Minutes were duly passed in the manner prescribed in the memorandum and articles of association of the Company (including, without limitation, with respect to the disclosure of interests (if any) by directors of the Company) and have not been amended, varied or revoked in any respect, (f) there is nothing contained in the minute book or corporate records of the Company (which we have not inspected) which would or might affect the opinions set out below, and (g) upon the issue of any Shares, the consideration received by the Company shall be not less than the par value of such Shares.

We consent to the use of this opinion as an exhibit to the Registration Statement and further consent to all references to us in the Registration Statement and any amendments thereto. In giving such consent, we do not consider that we are “experts” within the meaning of such term as used in the Securities Act, or the rules and regulations of the Commission issued thereunder, with respect to any part of the Registration Statement, including this opinion as an exhibit or otherwise.

Yours faithfully

/s/ Maples and Calder (Hong Kong) LLP

Maples and Calder (Hong Kong) LLP