A cup-shaped air bag is arranged on the upper portion of a tube body of the anal tube, an upper check ring is fixedly connected to the middle of the tube body in a sleeved mode, and a spring and a lower check ring are arranged on the lower portion of the upper check ring. The portion, above the upper check ring, of the middle of the pipe body is further sleeved with a pair of short pants, the twosides of the crotch of the short pants are each provided with a pull belt, the two pull belts penetrate through the penetrating and hanging holes in the left side and the right side of the lower checkring to lift the lower check ring, and then the lower check ring abuts against and pre-tightens the upper check ring and the pipe body through springs. After the cup-shaped air bag on the upper portion of the anal tube is inflated, the anal tube body can be effectively clamped in the rectum of a patient, and liquid is prevented from seeping along the tube wall; the middle part of the anal tube body is provided with an ejection device pulled by shorts to pre-tighten the anal tube from the outside; the pair of shorts is simple in structure and convenient to use, can effectively prevent the analtube from falling off automatically when the body posture of a patient is changed, and can adsorb excrement and liquid overflowing from the periphery of the anal tube to prevent the skin of the patient from being polluted and prevent a bed sheet from being contaminated, thereby greatly reducing the workload of nursing personnel.