Aimed at the failure of the main shaft fulcrum bearing on an aero-bearing test bench holding shaft and outer ring fracture,macro inspection of the bearing damage morphology,micro physical and chemical analysis of the fracture ring fractures,bearing working clearance calculation,lubrication inspection and the review of the test data during the test were carried out.It is found that the cause of the bearing failure is that the initial clearance of the bearing is not enough and the lubrication and cooling effect is poor,which cause large negative clearance in the bearing during operation,resulting in serious extrusion and wear between the rollers and ring raceways,and finally leading to the bearing holding shaft and instantaneous fracture of the bearing ring.The measures of increasing initial clearance and oil jet velocity,improving position of the lubrication nozzle were put forward and the test verification was carried out.The results show that the lubrication and cooling effect of the bearing is improved and the temperature rise is significantly reduced after improvement.