According to the requirements of National College Students Comprehensive Ability Competition in Engineering Training, a carbonfree car was designed which converted gravity energy into mechanical energy and drove the car to walk. NX10.0 software was applied for modeling design, assembling and motion simulation of the carbonfree car; the parts processing and assembly were finished according to the designed model; the prototype was tested, the track data were recorded and the results were compared with motion simulation.The results show that,the motion simulation basically conforms to the actual situation, which verify the feasibility of the design; the motion simulation results show the car can avoid the barrier pile spacing of 190~305 mm, and the test shows the car can avoid the barrier pile spacing of 180~350 mm, which meet the requirements of the design requirements 200~300 mm. It also provides a more convenient way for the later structural optimization.