Abstract: Today, as accident often happens when the elderly cross the road, designing a device which can prompt and exclude the potential risk around them when they are crossing the road is very necessary. This system selects 51 single chip microcomputer and the ultrasonic module of KS103 as the core. The external circuit is designed basing on digital tube, independent keyboard, buzzer and the temperature sensor of DS18B20 which was used to detect the temperature of external environment. When people are crossing the road, this product can calculate the distance and the speed of the vehicle automatically through the MCU and the ultrasonic module of KS103. Then it will calculate the time before the vehicle which keeps that speed comes here and display it by the digital tube. If it can’t meet the conditions that used to ensure pedestrians’ safety, the buzzer will alarm. So the accident can be avoided timely.