For two instant enterprise communication systems including instant communication server and client terminal, corresponding IP address is set for each instant communication server, and the instant communication servers communicate via network protocol and corresponding IP addresses to transmit and store structure architecture information of enterprise instant communication system. The client terminal in the instant enterprise communication system transmits information to the client termainal in other instant enterprise communication system via the instant communication server. The instant communication servers performs data communication via the user data protocol. Via small amount of altering to available instant enterprise communication system, the present invention can establish communication channel between different instant enterprise communication systems simply in low cost.