In traditional ciphertext database, the encryption and decryption method is not opaque to the upper application, short of independent key management mechanism and unable to manage multi-user security. In order to solve the problems, a new middleware system for ciphertext database was designed and implemented. Firstly, the encryption and decryption of sensitive data were realized by parsing and rewriting the datagram sent by database client or database server. Then, key management was realized by setting up independent key management module and using secondary key management. Finally, through the independent user management module, the management of users in ciphertext database was realized by means of user authority judgment, identity dynamic authentication, user identity cancellation and update. The experimental results show that, compared with the traditional ciphertext database, the proposed middleware system has better security, and its transmission efficiency is constantly improved with the increase of data volume. The proposed middleware system can effectively guarantee the security of ciphertext database and has high data transmission efficiency.