The utility model discloses a power-assisted bicycle damping device which comprises a main bicycle frame and an auxiliary bicycle frame, a driving motor is installed in the main bicycle frame, output shafts are arranged on the two sides of the driving motor, the exteriors of the output shafts are connected through U-shaped clamping grooves, the main bicycle frame is provided with a bicycle frame rotating shaft fixing seat, and the bicycle frame rotating shaft fixing seat is connected with the auxiliary bicycle frame. The auxiliary frame is provided with an auxiliary frame rotating shaft, the frame rotating shaft fixing seat is rotatably connected with the auxiliary frame rotating shaft, the axis of the output shaft is overlapped with the axis of the auxiliary frame rotating shaft, and the output shaft and the auxiliary frame rotating shaft which are concentrically and non-coaxially arranged can ensure that the auxiliary frame rotating shaft is not in contact with the auxiliary frame rotating shaft when a vehicle jolts. The output shaft and the auxiliary frame rotating shaft move in a split mode, synchronous movement between the output shaft and the auxiliary frame rotating shaft is avoided, breakage of the output shaft in the long-term use process is avoided, and therefore the service life of equipment is prolonged.