Abstract: This paper analyzes the causes of abnormal temperature rise of the main shaft bearing during the operation of a wind farm. Through the inspection of the main shaft bearing of the wind turbine, the analysis of the wear of the bearing parts, the analysis of the lubricating grease, and the comparison of the bearing temperature during the operation of the wind turbine, it is judged that the main reasons for the wear of the main shaft bearing and the failure of the cage are the deterioration and failure of the grease quality. By expounding the working maintenance of lubricating grease and the key points of operation and maintenance of main shaft bearing, carry out fault summary and analysis, formulate relevant corrective and preventive measures, and avoid similar faults of fan bearing。