In this paper,the automobile-reversing rader system which uses the single chip as core is introduced.The system uses the ultrasound to realized distance measurement without contract.The system mainly includes the blast-off receiving and temperature measurement electric circuit.The temperature measurement circuit which uses a digital sensor DS18B20 is given.The accurate degree of distance is compeleted.This system is suited to mesure distance which below 5 meterses can meet the safety requestment of reversing a car.