Abstract: In view of problems of short transmission distance, low communication rate, high cost and difficult maintenace existed in traditional water supply controller caused by networking mode of serial port, the paper proposed a new networking design of remote control system of water supply controller based on serial server. It introduced networking process, communication protocol and design of communication software taking CPS-21c water supply controller with frequecy conversion and constant pressure as an example. The actual application showed the system is stable in transmitting data and easy in operation, which greatly improves control efficiency.