Abstract: In order to improve the security of data storage in cloud computing, a chameleon Hash authentication tree optimized audit method for data storage security in cloud computing is proposed. Firstly, an optimized public audit protocol is proposed. The validator homomorphic linear stored as user data on the TPA site, the cloud storage server (CSS) the size of the optimal response. At the same time, the query request of CSS is optimized by using quasi random function; Secondly, using chameleon hashing and an improved chameleon authentication tree, efficient dynamic data updates are performed on the client data (cloud), supporting block level updates and fine grained updates; Finally, through thorough security and performance analysis, it is proved that the proposed method is secure and efficient.