This paper，based on the signal transmission theory，examines whether the corporate social responsibility（CSR）assurance can provide incrementally useful information to investors by investigating the changes of properties of the analyst earnings forecasts by using the data from the A shares of Shanghai and Shenzhen of non financial listed companies from 2008 to 2014.The empirical results are as follows：First，the CSR assurance can reduce the analysts forecast error and dispersion.Second，the positive impact of CSR assurance on analyst earnings forecast accuracy is stronger for non state owned enterprises and companies located in regions with better institutional environment facilities.Further，on the basis of the former two categories，we group the samples according to the releasing form of CSR and find that these results are only maintained in the firms releasing the CSR compulsorily.These results hold water after we control the endogenously problem.Our findings suggest that the CSR assurance can improve the quality of non financial information of the company effectively and provide incrementally useful information to investors.The conclusions of this paper enriched the literature of economic consequences of CSR assurance，and it is valuable for policymakers to improve the CSR disclosure system.