A position limitation protection type ani sphincter prosthesis comprises an upper fixed ring arranged on an upper ring sleeve in a sleeving mode, a movable middle ring arranged on a middle ring sleeve in a sleeving mode and a lower fixed ring arranged on a motor sleeve in a sleeving mode, wherein the upper fixed ring, the movable middle ring and the lower fixed ring are sequentially connected, the upper ring sleeve is axially connected with the middle ring sleeve, a reduction gearbox connected with a motor is arranged between the middle ring sleeve and the upper ring sleeve, the movable middle ring is connected with a reduction gear train in the reduction gearbox through an inner gear ring arranged on a gear ring sleeve in a sleeving mode, a Hall element is arranged on an upper cover plate of the reduction gearbox, and two magnets matched with the Hall element are arranged at the opposite ends of the gear ring sleeve and the upper cover plate of the reduction gearbox in a spaced mode. It can be effectively avoided that intestines are damaged due to the too large swing amplitude of a swing arm of the middle ring, a mechanical is stuck due to the overturning of the motor, and the motor is burnt down due to the too large current; the opening and closing amplitude of the prosthesis can be adjusted by a mechanism according to the feeling of human intestines; the whole device is simple in structure, small in size, light in weight and beneficial for increasing the transplanting success rate.