In order to find out the real velocity of the small multifunctional chassis so as to improve the work efficiency and quality, a set of measurement system was designed. The system uses STC89C51 microcontroller and peripheral hardware circuit as hardware platform and employs the serial communication technology and C language software programming techniques. The velocity measured was displayed on the LED digital tube. The system has strong anti-interference capacity and ultra low power consumption. The experimental results show that this system is precise in speed measuring, and the average accuracy is 98.2%, which can meet the requirements on the design speed of the system.