Abstract: The fundamental principle of bond graph theory was stated in this paper, and then the theory was applied to design a complete bond model of electric vehicle motor powertrain system according to the analysis on dynamical performance and interaction of each unit in the power train system for electric vehicle, and the state equations of system were established. Finally the bond model was simulated by Matlab software. The simulation result shows that the bond graph is a valid method to integrate both bond graph theory and SIMULINK simulation into system dynamics analysis can be applied to dynamics modeling and analysis of vehicle power transmission.