Auditing is one of the most important corporate governance mechanisms and helps to improve firms performance. Social responsibility report auditing positively improves CSR (Corporate Social Responsibility) information quality by supervising, risk evaluation and strategic planning. Data taken from listed firms in Shanghai and Shenzhen stock exchange between 2010 and 2013 indicate that the auditing of CSR report has a significant positive effect on CSR information quality. Furthermore, the positive effect of CSR report auditing on CSR information quality is greater when the large shareholder has a greater supervision motivation. Moreover, the supervision of large shareholders is more effective in private enterprises than in SOEs, which means large shareholders in private enterprises helps to strengthen the CSR report auditing effectiveness in greater extend. This article is of great significance in promoting the theoretical and practical development of CSR report auditing.