This article focus on the relationship between company performance and ownership structure. The sample covers 1088 Chinese private companies listed in Shenzhen and Shanghai Security Exchanges between 2003 and 2012. To test Demsetz’s endogenous hypothesis, we compared the results obtained by OLS and TSLS respectively, the great diversity indicates that ownership structure is truly an endogenous variable. Following two agency problem theory, ownership structure is considered as ownership concentration and manager ownership two aspects. Empirical findings considering the endogenous property suggest that there is a mutual positive correlation between company performance and ownership concentration. Another interesting result is that higher company profitability requires a higher equity proportion of managers which go decrease as company has a better performance.