The invention discloses a power device and belongs to the technical field of mechanical transmission. The power device includes a motor and a gear box. The motor has a motor shaft. The end surface ofthe motor shaft is provided with an inner tapered hole. The gear box includes a box body and an input gear inside the box body. The input gear includes a gear body and a support shaft on one side of the gear body. The support shaft has an outer tapered surface in interference fit with the inner tapered hole. The motor shaft and the input gear are separated such that the outer diameter of the gearbody of the input gear cannot be restricted by assembly problems, thereby achieving a wide application range. During production, the motor shaft and the input gear can be machined and heat treated separately, which reduces production costs. During assembly, the support shaft of the input gear is pressed into the inner tapered hole on the motor shaft by external force. Since the outer tapered surface and the inner tapered hole have conicity, the press-fitting stroke of the interference fit is made short and to have less damage to parts and a long service life.