The rubber band used in anal fistula surgery usually serves two purposes, one is used to hang the thread and the other is used for drainage. For high complex anal fistula, the rubber band used often play the role of hanging line. What is called high complexity fistula. It is the fistula of the inner mouth over the anorectal ring, if this time a one-time cut, the sphincter between the inner and outer mouth is likely to cause anal incontinence, at this time it is necessary to use a rubber band to hang the line. Its purpose is to protect the function of the anorectal ring through the slow cutting effect of the rubber band, in order to prevent the anal incontinence caused by. Then what is called drainage with rubber bands, that is, the scope of the anal fistula is large, in order to protect the muscles and skin around the anus, at this time we need to use rubber bands to drainage.