The invention discloses a rotor, bearing and retaining ring assembling device. The rotor, bearing and retaining ring assembling device comprises a worktable, an assembling die, a press-fit cylinder, arotor storage rack, a rotor feeding device, a bearing feeding device and a retaining ring feeding device. The assembling die is provided with a retaining ring slide and a bearing slide, an assemblinghole is formed in the top of the assembling die, a bearing push hole and a retaining ring push hole are formed in the side surface of the assembling die, a bearing cylinder and a retaining ring cylinder are arranged on the worktable, a bearing push plate is fixedly arranged at the output end of the bearing cylinder, a retaining ring push plate is fixedly arranged at the output end of the retaining ring cylinder, and the assembling hole penetrates through the end point of the bearing push hole and the retaining ring push hole. The rotor feeding device vertically places a rotor above the assembling hole, the bearing feeding device and the bearing cylinder push a bearing into the assembling hole, the retaining ring feeding device and the retaining ring cylinder push a retaining ring into theassembling hole, and then the press-fit cylinder presses and installs the rotor, the retaining ring and the bearing together. The bearing and the retaining ring are automatically assembled to the rotor, and the assembly efficiency is high.