Abstract: In order to realize the efficient matching of the pure electric vehicle powertrain system and maximize the utility of the key components, the optimization of the vehicle power and economy is studied. Through the analyses of the industry standards for electric vehicles and vehicle parameters, the basic performance parameters of XH2 electric vehicle are determined. The optimization scheme that sets the gear ratio of powertrain as an optimization variable has been determined via the previous matching and selection work. With matlab software, the multi-objective optimization mathematical model for powertrain system is established, and four solving nonlinear manners are used to solve this model through setting objective functions, comparing and analyzing the results. Consequently, the optimal scheme for vehicle gear ratio is derived, and the performance of power is improved largely while the performance of economy is raised slightly.