Based on Shanghai and Shenzhen A-share listed companies in which M&A events occurred from 2007 to 2010, this paper makes a study on the relationship between the managerial ownership and the M&A performance, and we find that there is no significant relationship between the managerial ownership and the short-term M&A performance, but a non-linear relationship between the managerial ownership and the long-term M&A performance. Further, we validate that accounting conservatism can reduce the agency conflicts between managers and shareholders, and find that compared with the acquires with higher accounting conservatism, there is a more obvious relationship between the managerial ownership and the long-term M&A performance in the acquires with lower accounting conservatism. These findings mean that the managerial ownership will not have a significant impact on performance in short term after the merger, but will take some time to be revealed later, and there are different influence degrees due to different accounting conservatism among companies.