Abstract: Under the mutual identity authentication, a scheme based on distributed cloud storage system was proposed, using symmetric encryption algorithm and hash function to realize bidirectional authentication process. Advantages of the novel project are to produce fair session key to both communications, and design the two different types of authentication: within the network and across a network authentication. Then the security of this scheme was analyzed. The scheme is more secure than the former ones and it can protect the privacy of users and non-repudiation, and has lower computational cost. Therefore, this scheme can meet the demand of cloud storage communication environments.