本文介绍了基于微处理器控制的汽车倒车雷达预警系统，由微处理器控制时间计数，计算超声波自发射至接收的往返时间，利用声波在空气中的传输速度，从而得到实测距离，并根据障碍物与车尾的距离远近情况发出报警等级。关键词：微处理器 超声波换能器 超声波测距 预测控制Abstract：This paper introduces the design of warning system for Radar in Back Car based on miroprocssor．The microprocessor control the time and transmitting and refleting back of ultrasonic，the distance can measure through calculating the speed of ultrasonic in car．The system can alert according to the changing distance．Key words：microprocessor ultrasonic wave transducer ultrasonic distance measuring