The intimate partner relationship between the underwriter and the auditor has always been controversial．We define the auditor who serve as a fixed partner of an underwriter as the underwriter-accountant，and use Chinese IPO firms from 18 May 2001 to the end of 2011 as our sample toinvestigate whether the underwriter-accountant is the result of cooperation or collusion． We find that the underwriter-accountants can significantly decrease the degree of earnings management of IPO firms，and that the restriction effect，reaching the maximum in about 6 times，would be strengthened with the increase in the number of cooperation． These results suggest that the underwriter-accountant represents an effective cooperation relationship based on the repeated game between the underwriter and the auditor． In this way，the transaction costs of joint production among financial intermediaries can be reduced，the earnings management of IPO firms can be restricted，and the healthy development of capital markets can be enhanced．