Abstract: According to the characteristics of city transportation, on the PC-PLC network platform, adopting an original uniform line control technology to multi-crossroad, we implement an intelligent and coordinative control to the signals of the city traffic trunk line. This control system effectively reduces the latency time of vehicles and increases the traffic flux of the trunk line. Results of the emulation make clear that this method of intelligent control distinctly overmatches that of one-point control to improve traffic capacity, and consequently provides a novel approach to settle city traffic problem.