A vehicle driven by gravitational potential energy which control the direction by itself is developed based on the requirement of National Undergraduate Engineering Training Comprehensive Ability Competition. The vehicle can run in “S” track automatically and bypass equidistance obstacles on the track, and adapt the spacing change of obstacles through adjusting structure parameter. Through carefully design and detailedly analysis of vehicle mechanical system, investigates the issues of improving vehicle running accuracy and stability from aspects of vehicle structure, assembly and adjustment. The experimental result shows that the vehicle has the advantages of simple structure, stable operation, accurate trajectory and smooth obstacle-crossing by“S”track, which provides reference for the vehicle design and working performance improving.