An optimized mathematical model for vehicle powertrain was introduced,considering comprehensively the dynamic property and the fuel economy.Taking fuel economy and dynamic property of the vehicle as optimal goals the powertrain parameters of the vehicle were optimized based on a nonlinear programming genetic algorithm.And the results were verified by simulation tests.The optimization results show that the acceleration time from standstill decreases by 3.96% and the fuel economy of the commercial vehicle decreases by 8.32% per 100km.The feasibility of the method based on nonlinear programming genetic algorithm was then proved.