Abstract: However，vibration and noise (NVH) issues caused by the high-speed operation of the P3 motor have become one of the key factors limiting the improvement of the hybrid transmission’s performance. This paper focuses on the NVH improvement of hybrid transmissions, with an emphasis on studying the noise sources of the P3 motor under high-speed conditions. It proposes a comprehensive strategy for precise optimization of the MASTA through gear design，process optimization，manufacturing precision control，and DOE methods. By increasing gear overlap，optimizing shape errors and their directional control during the manufacturing process，improving micro parameters of the gear teeth，and combining experimental design methods for systematic optimization，the NVH performance of the hybrid transmission has been significantly enhanced.