The invention discloses a clamping device for motor shell boring. The clamping device comprises a base and a clamping jaw disc; a fixed support frame is arranged at one end above the base; a controller is arranged beside the fixed support frame; a bearing base is arranged above the fixed support frame; a rotating shaft is arranged in middle of the bearing base; the clamping jaw disc is arranged at the front end of the rotating shaft; three inner clamping jaws are arranged at the periphery of the clamping jaw disc; an electromagnetic valve is arranged at the back end of the bearing base; a transverse guide rail is arranged above the base; a movable base is arranged on the transverse guide rail; a movable support frame is arranged above the movable base; a dial is arranged on the side surface of the movable support frame; and a locking nut is arranged on the inner side of the dial; and a hand wheel is arranged on the outer side of the dial. The clamping device has the following beneficial effects: a motor shell can be machined only through once fixation, so that the operation is simple and convenient; and adjustment of the machining position is convenient, so that the labor intensity is reduced, and the machining precision is improved.