In order to research the vibration and noise reduction in pure electric vehicle power-train, a comprehensive work is to simulate the power-train incentive of a high-speed pure electric vehicle, and indicates significant impact of gear mesh system on the power-train NVH performance. Therefore, it is necessary to further study the impact of meshing gear system on electric vehicle power-train vibration and noise performance and seek reasonable methods to reduce the vibration and noise. In this paper, a typical pure electric vehicle's powertrain was used to conduct vibration and noise dynamic simulation. Firstly, the power train model was established considering the gear meshing stiffness, transmission errors, bearing factors and shell flexible, then the vibration and sound radiation dynamic response of power-train was simulated. Based on the accuracy of prediction model, a gear tooth modification was carried out for vibration and noise optimization. After the modification, vibration amplitude of power train surface reduced 0.2~0.6 m/s2, and sound pressure level of the far field reduced accordingly. The result shows that the teeth micro modification is an effective way to reduce transmission error and dynamic load of bearings, as well as improve uniformity of tooth load. Meanwhile, the established model provides a powerful simulation platform for further optimization and improvement.