Nowadays,many enterprises and personals are inclining to outsource their data to public clouds,but security and privacy are two critical problems that they cannot ignore.Not only kinds of thieves may break the door of cloud provider.but also the providers itself also want to dig into the data to find valuable information.In this paper,we propose a secure and efficient storage system which distributes files in several clouds and allows users to search the files securely and efficiently.In the proposed system.keywords are transformed to integer values and secretly shared in a defined finite field.then the shares are mapped to random numbers in specified random domain in each cloud.Files are encrypted with distinct secret key and scattered within clouds.Information about keyword/filc is secretly shared among different cloud providers.Legal users can search in the clouds to find correct encrypt ed files and reconstruct corresponding secret key.No adversary can find or detect the real file information even they can collude all the servers.Manipulation on shares by one or more clouds can be detected with high probability.The system can also detect malicious servers by introducing virtual points.