Hybrid system has the advantage of energy conservation and environmental protection. To improve the fuel economy of a hybrid system，based on the structure of the ISG velocity coupling HEV(hybrid electric vehicle)，a dynamics simulation model is built. By using dynamic programming(DP) global optimization method，the variables of the engine throttle and the motor torque are set as the control variables，and the engine speed and the battery SOC are set as the state variables，the engine fuel economy is set as the objective function，and the battery SOC balance and the limited frequent shifting are set as the additional cost function. Then a global optimization program is built，and the simulation results indicate that the fuel economy of DP control HEV is 35.5% more efficient than that of the conventional vehicle.