A small crack behind the anus is considered to be suffering from anal fissure, which is a small ulcer formed due to fissure of the skin of the anal canal, below the dentate line, due to various reasons. The disease is most common in young and middle-aged patients, the direction is parallel to the longitudinal axis of the anal canal, oval or shuttle-shaped, accompanied by severe pain. The cause of anal fissure is complex, and the treatment of anal fissure is mainly divided into conservative treatment and surgical treatment. Conservative treatment is in principle to relieve sphincter spasm, relieve pain, help defecation, interrupt the vicious cycle, and promote local healing, the main method is to use 1:5000 potassium permanganate warm water sitz bath after defecation, keep local clean, oral laxative or liquid paraffin, so as to make stool loose and lubricate, and keep the bowel movement smooth. After local anesthesia for anal fissure, the patient is lying on the side, first show the finger to expand the anus, and then gradually extend the two middle fingers to maintain the expansion for 5 minutes, after the expansion, it can relieve sphincter spasm, expand the trauma and promote wound healing, but the recurrence rate is relatively high, and at the same time, it can be complicated with hemorrhage, perianal abscess, and fecal incontinence. Surgery: There are two main surgical methods for anal fissure, one is anal fissure excision surgery, the disadvantage is that the healing is slower; the other is the internal anal sphincter cut off surgery, the method has a high cure rate, but improper surgery can lead to anal incontinence.