Abstract: Database as a Service(DBaaS) is becoming a research hotspot of cloud computing,as a main application domain,business database application hosting puts forward the requirements of isolation and privacy preservation on hosting data．To satisfy this requirement,this paper proposed a virtual machine based database hosting method and corresponding DBaaS system based on CryptDB．This system has realized the hosting data encrypted storage and can execute SQL queries based on encrypted data．The experiment shows that compared with fully homomorphic encryption system,the performance of the system has lower loss,and better solve the issue of privacy protection and practical.

Key words: Database as a service,Privacy preservation,CryptDB,Virtual machine