Abstract：In the recent years, the traffic condition becomes increasingly crowded in Chinese cities. Tail-crash and reverse-collision take place every now and then in the daily drive, which cause damages to a rear bumper or even the body of vehicle. A finite element model of one vehicle was established and the protective performance of the rear bumper in the vehicle was studied from the energy absorption and body protections for the vehicle under the condition of rear-end accidents with a low speed. As a result of the environmental protection and the energy conservation, automobile lightweight already became the tidal current of the world automobile develops. Under the condition guaranteed the safety performance of the vehicle, the automobile should work towards light weighed target improvement. According to the simulation results, the material used for the beams on the rear bumper were modified to high-tensile steel, which made the crashworthiness of rear bumper remarkable improved. The result indicates that the bumper system after modified not only satisfies the requirements of the collision law and regulation, but also makes the weight of the bumper system reduce by 45%.