Abstract: To solve the problems of data security and distributed data management that existed in SaaS platform, the paper puts forward a system application framework based on open SaaS service platform architecture. On the basis of this architecture, the paper gives abstract modeling on data application, which uses the idea of optimizing cache management strategy to solve data access problem in network environment. Combining with traditional LRU arithmetic and SIZE arithmetic, the paper gives a LRU-SIZE arithmetic which is effective on the management of data access of the open SaaS service platform. The combination of open SaaS service architecture and LRU-SIZE arithmetic can solve the problems of data access and data management of enterprise effectively. Meanwhile, it can improve the application experience of users.