Abstract: Equity structure directly affects the quality of internal control, which guarantees the performance of companies. After making an empirical analysis of the triangle relations among equity structure, internal control and company performance on the basis of the data for three successive years(2009—2011) of Jiangsu listed companies in Shanghai stock market, the essay comes to a conclusion that four variants, that is, the equity structure of the top ten share holders, the Herfindahl-type of index, Z index and the internal control index, of the top five share holders, exert conspicuous influence on the performance of companies and accordingly offers some effective means to improve performance of Jiangsu listed companies in Shanghai stock market.