The invention relates to a detachable shaft dynamic balance tooling device for a large motor, which is composed of a shaft, a conical ring and fastening bolts, and is characterized in that a taper journal 5 matched with the chamfer angle of the inner diameter end face of a detachable shaft 4 is machined at one end of the shaft 1; the other side of the shaft 1 is provided with a protruding large diameter 6, threaded holes 7 are evenly distributed in a certain pitch circle of the outer side surface of a protruding part of the protruding large diameter 6, the fastening bolts 3 are assembled on the threaded holes 7, the protruding outer side of the protruding large diameter 6 is provided with a transition shaft shoulder, and the shaft 1 is in sliding fit with the conical ring 2. According to the invention, the detachable shaft dynamic balance test work of the motor is realized, the workload and the working time are reduced, and the working efficiency is improved. Meanwhile, the accuracy and the convenience of the detachable shaft dynamic balance test are ensured, and the operation is simple and convenient.