In the permanent magnet synchronous motor speed control system, under the VB environment, Use the RS- 232 / RS - 485 serial communication which is used by the MODBUS to make the computer(pc) communicated with the TMS320F2812. Expounded software design of the host (pc) which is in the VB environment and communication with TMS320F2812, by a way of communication with the crc check, to ensure the reliability of communication, fully uses system resources ratio nally, raise efficiency and characteristics of com munication. Meantime, use the function of VB’ store data, we can find out the historical data of motor easily. Through practical operation, based on vb environment, use of serial communication system has high relIab ility and practicability.