A remote monitoring system of rectifier based on an improved heartbeat mechanism was developed according to quickness and stability of remote TCP/IP communication. Different heartbeat mechanism was designed at server and client, and server and client can judge the states of network connections through transmitting heartbeat packets between server and client. The mechanism can request to reconnect with remote clients or server when network is at the jam and inform users when network is at the disconnection. The mechanism was realized by using Socket with the model of single server and multi clients. The heartbeat model had been applied to a remote monitoring system of rectifier based on Client/Server model. The testing result of system and model shows that the heartbeat model has better performance and improves the availability and dependability of the system.