Data security and virtualization security issues are two key bottlenecks restricting the application of cloud computing promoting and applications, especially for the Cloud-based media computing system. In this paper, states of the art of the techniques on cloud computing data security issues, such as data encryption, access control, integrity authentication and other issues is surveyed, on this basis, the key technical issues of the cloud computing data security should concern about and focus on are indicated, and some corresponding countermeasures and suggestions are presented. For the virtualization security problem introduced by private cloud computing, the security risks induced by virtualization are analyzed and classified, and then based on the divide-conquer idea, for each kind of security risk, some corresponding solutions are presented.