Abstract: The structural characteristics, main damage forms and failure causes of the main reducer bearings in automobiles are elaborated in detail. Through the analysis of actual failure cases, the influencing factors of bearing metallurgy and heat treatment quality are excluded. By using the longitudinal section metallography and hardness test results of bearing parts, the heat sources of bearing part deformation and temperature rise are quickly determined.Finally, by studying the unique lubrication oil circuit design of the automobile main reducer, it is found that the disconnection of the oil circuit is the main cause of the high-temperature adhesive wear failure of the bearings.