Based on the "magnetic train" phenomenon in inhomogeneous magnetic field and the Lorenz formula 　　and the magnet force formula，we derive the balancing speed formula of car. The experimental result shows that the 　　numerical parameters in the expression by MATLAB and COMSOL software combined with MATLAB for plotting v 　　( balanced car speed) ，and U0 　　( battery voltage) ，v and the coil radius of R，v and n( the number of turns of the coil 　　density) ，V and N( the number of magnet is added) diagrams，and those relationship are agreement with the experimental 　　exploration.