Aimed at the failure problem of grease-lubricated bearing used in aeromotor during the test，the reasons of the bearing damage were analyzed from five aspects，including the appearance，material，hardness，microstructure and grease.It is found that the main reason for the bearing failure is that the wear debris generated by the wear of the seal ring falls into the bearing and cause the deterioration of the grease.The improvement measures such as changing the sealing ring material from polytetrafluoroethylene to fluororubber with lower hardness and reducing the interference between the contact lip of the sealing ring and the inner ring flange are proposed,and good results are achieved.