Abstract: Taking tooth surface load distribution and gear transmission error as the optimization objectives, the effect of gear micro modification on the vibration and noise of two-speed automatic transmission system was analyzed and compared for electric vehicles. A Rigid-flexible coupling dynamic model was established for the rotor and transmission of the motor. Taking the vibration acceleration at the bearing of the transmission as the excitation, a near-field sound radiation cloud and radiated sound power of the transmission under rated operating conditions were calculated. The results show that the radiated noise of the gearbox after gear modification can be well suppressed, providing reference significance for the optimization of the transmission and reduction of the vibration and noise of the transmission.