十字路口车辆穿梭，行人熙攘，车行车道，人行人道，有条不紊。那么靠什么来实现这井然秩序呢？靠的就是交通信号灯的自动指挥系统。交通信号灯控制方式很多。本系统采用MCS-51系列单片机AT89C51为中心器件来设计交通灯控制器，实现了能根据实际车流量通过8051芯片的P3口设置红、绿灯燃亮时间的功能；红绿灯循环点亮，倒计时剩5秒时黄灯闪烁警示（交通灯信号通过P1口输出，显示时间通过P0口输出至双位数码管）。本系统设计周期短、可靠性高、实用性强、操作简单、维护方便、扩展功能强。 -The intersection vehicles shuttle, the pedestrian is bustling, car dealership traffic lane, person sidewalk, methodical. Then depending on what to realizes this orderly order?　the traffic lights on the automatic control system. There are great number kinds of modes to control the traffic lights. The system uses a series of MCS-51 as the center AT89C51 single-chip device designed to control the traffic lights, so as to realize the function of setting red, green light time by 8051 chip’s P3 port according to the actual traffic flows, lighting the red-light and green-light by turn and lighting the yellow-light to warm while 5 seconds left(outputting the traffic light signal by P1,outpuing the time by P0 and showing the time on double-digits nixie tube). Short of the design cycle, high reliability, practical, simple operation, easy maintenance, the expansion of powerful is this system.