in recent years, our country with the increasing demand of urban rail subway products, the user's requirements are also gradually increase, in the process of vehicle delivery, product quality problems timely also appears especially important, and these problems in the comparatively typical problems for the gearbox oil emulsification, vehicle arrives the user site, the vehicle after the commissioning, the oil emulsion. Resulting in strong dissatisfaction of the user, and there is still emulsification after the replacement of oil. The problem led to user complaints.