As one of the key components of new energy vehicles,how to improve the load sharing characteristics and NVH performance of gear boxes has become a hot issue in the new energy vehicle industry.The gear modification parameters were calculated by using the gear modification method,taking into account the elastic deformation of the gear and shafting as well as the manufacturing and installation errors of the gear.The gear box simulation model was built by using the gear design and analysis software,and the changes of gear contact stress,transmission error and transmission efficiency before and after modification were simulated and analyzed.The prototype of gear box was further made and its transmission efficiency was tested.Compared with the simulation results,the reliability of gear modification was verified.The results show that the gear modification can reduce the contact stress on the tooth surface,uniform the load on the tooth surface and reduce the peak value of transmission error.The efficiency test results are basically consistent with the simulation results.