In industrial control, for the problem of controlling the actuator directly by PC and data processing, we design the serial communication system by using RS232 serial cable to connect PC and CPU board. By using the Windows Forms module of .NET Framework and the properties、events and methods of its commonly used controls, we design the PC software. It can realize the goal of downloading compiled files from PC to CPU board,sending function commands,receiving response data, and it has realtime display for communication process. Practical use verifies that the serial communication of this system is correct, It has a friendly interface，advantages of strong function and easy operation，and good practicality.