This paper examines the market’s reaction to voluntary disclosures of internal control self-evaluation reports and assessment of the CPAs firm by firms listed in Shanghai Stock Exchange from 2006 to 2008. For the control firms, we use firms with the same industry and size that listed in SSE not disclosing the self-evaluation reports from 2006 to 2008 and listed in Shenzhen Stock Exchange mandatorily disclosing the self-evaluation reports from 2007 to 2008. We find that the market reaction is positively associated with disclosing internal control information and the cumulative abnormal return (CAR) is positive. Firms with voluntary disclosure have higher CAR, while firms with mandatory disclosure have lower CAR. However, the information disclosure has its limits. In long event window, the CAR of companies with internal control disclosure is on a decrease; even there is a reversal effect. At the same time, the size of the listed companies and whether it is audited by "the big four" etc. also influence the CAR of companies with internal control disclosure. The research results show that the government should uphold the principle of internal control disclosure, especially the mandatory disclosure, and encourage the listed companies to do so voluntarily. The listed companies should be careful about the context and form of disclosure, and keep the balance between disclosure and commercial confidentiality.