This paper focuses on studying cloud storage data protection model and implementing encrypted storage of user data in double-key form. User data are encrypted with symmetric encryption algorithm and this secret key is encrypted with asymmetric encryption algorithm. The private key is managed and controlled by users. In this way, users guarantee the security of their own data with the sole private key. Providing effective protection for uploading and downloading of user data and good data storage and transmission support for cloud storage application through the data protection mechanism deployed at client, thus solving the biggest obstacle, i.e. security of cloud data in the application of cloud storage enterprises currently to a certain extent.