The single machine press fitting efficiency of the end cover assembly of the wheel hub motor is low and the process is scattered.Based on analyzing the structure and press-fitting process of the end cover assembly of the wheel hub motor,a “bearing-end cover-oil seal” integrated press-fitting device was designed.In the press-fitting device,the bearing grasping mechanism used the friction between the O-ring and the bearing inner ring to grasp the bearing.A method for O-ring selection calculation and groove design using Lindley formulas and empirical formulas according to the required friction force was proposed.The prototype was trial-produced according to the simulation plan.The test results show that the designed bearing grasping mechanism can be used to realize the stable grasping and pressing of the bearing and the automatic separation from the bearing after pressing.