The invention provides a device for preventing the deformation of the stator of a motor and a manufacturing method thereof. To the device, a stator formed by laminating multiple stamped steel is provided with at least two through holes penetrating through the stamped steel, the through holes are evenly arranged out of the effective external diameter area of the stator, and key steel for preventing the deformation of the stator is respectively arranged in the through holes; the manufacturing method of the device is as follows: firstly punching holes on the stator, laminating the stamped steel in order and then welding into a whole, and then correspondingly knocking the key steel in the multiple stamped steel. After the device is added on stators of small and medium motors, the periphery ofthe stator is welded and the key steel is knocked in, the strength of the stator can be effectively improved to prevent the deformation of the stator, and meanwhile, the strength of the stator is ensured and a motor engine seat is omitted simultaneously, thus the appearance of the motor is better and the structure is simpler, thereby being applicable to the field of small and medium motor. The device in the invention has simple manufacturing method in which only the steps of punching holes and knocking key steel in the original stator structure are needed, and the manufacturing process is simple and feasible without influence on the original structure of the motor.