Abstract: To solve the problem of vibration and noise of a new pure electric vehicle gearbox, considering the influence of gear transmission error,a two speed gearbox simulation model was proposed for the dynamic analysis of the transmission system. A block Lanczos method was used to solve the modal frequencies and modes of the gearbox. By using the coupled acoustic boundary element method, the dynamic analysis results were taken as the excitation to solve the radiation sound field of the gearbox, and the gear of the gearbox was optimized. The simulation and experiment results show that, the method can improve the vibration and noise of the gearbox obviously.