With a power-split hybrid electric vehicle（ HEV） as the research object,the characteristic parameters of the planetary gear in the coupling mechanism and the main reduction ratio are optimized on the basis of double objective function for performance economic and dynamic. The hybrid vehicle model is established by the vehicle simulation software AVL/Cruise and the control strategy is designed by MATLAB/Simulink,combing with the optimization software Isight,the optimization model is created. The non-dominated sorting genetic algorithm is applied to optimize the characteristic parameters of the planetary gear and main reduction ratio. The maximum vehicle speed is the dynamic objective and the economic objective is the fuel consumption performance. Compared the result of simulation in different parameters indicate that the equivalent fuel consumption per hundred kilometers of HEV decreased by 10% after optimization in the condition of strategy and vehicle dynamic requirement both unchanged.