Abstract: In view of the prolems that due to the insufficient adaptability of the traditional traffic light control mode, it is difficult to match the growing demand for traffic services and the continuously rising traffic pressure, and is prone to lead to low intersection traffic efficiency, increased traffic delay and others, improving the smoothness and efficiency of intersection traffic are took as the goal, optimization and transformation are conducted on the traditional signal control mode. Taking S7-1500PLC as the core controller and combined with HMI human-machine interaction interface, a set of traffic light automatic control system is designed. Through the PLC logical operation capability and the HMI visualization interaction function, this system achieves flexible adjustment and real-time monitoring of signal light control strategies, providing a new technical scheme for solving the difficult intersection signal light control problem at urbans, and is expected to improve the operational efficiency and service quality of urban traffic.