A traffic light simulation system based on 51 single chip micro-computer is introduced. The circuit is described from two aspects such as hardware circuit and software program designs. Hardware circuits are also described from the functions of clock circuits, reset circuits, power supply circuits, LED display circuits and digital tube countdown circuits. When the software program is written, the circuit is debugged with the actual traffic light requirements, and the expected effect is achieved. Prior to the design of the circuit, Protues simulation software and Keil software are used for joint modulation, and the feasibility of the circuit is verified and the working efficiency is greatly improved.