ERP is now facing serious challenges and difficulties under the networked and global manufacturing, to solve the complex development and application problems of Enterprise Resource Planning (ERP). There are some shortcomings raised due to the huge amount of resources required for the implementation and big risk of failure, it needs the cloud computing. ERP system based on cloud computing is put forward and several key technologies are discussed in this study. The concept and characteristics of cloud ERP are defined and the architecture of service-oriented ERP in sale force platform based on cloud computing is proposed. The aim in this paper, it established the theoretical and technological support for helping to construct the cloud ERP system from old ERP system under force.com platform.