Abstract: In the traditional cloud storage system which supports dynamic operations, the computing and communication cost derived from the dynamic operations to the file is undertaken by the user completely. It brings user the corresponding pressure on computation and communication. In order to solve this problem, we design a provable data possession scheme via third-party proxy dynamic operations in clouds. In this scheme we bring in a powerful third-party auditor, the users can delegate it to perform the audit and fulfill the dynamic operations. In this processing, the system can ensure the user's data privacy in the third party auditor. Finally, the security and performance analysis show that our scheme can complete the audit task efficiently and securely.