This paper develops an active network security protection system based on mobile devices on Android system. The hardware of the system consists of database encryption module, certificate management module, database encryption technology architecture, key management module and so on. In the aspect of software, the database system is used and the secure encryption algorithm is designed. Thus, the security and reliability of data are guaranteed. The system realizes the fast, convenient and low-cost processing of business data flow. It monitors and prevents the data flow, and realizes the real-time monitoring and prevention of the data flow. Experiments show that the cryptosystem based on key store can effectively improve the capacity and security of cryptosystem.