Perianal abscess becomes anal fistula after surgery mainly because the site where the abscess occurs is connected to the anorectum, and the abscess shrinks after surgery to form a granulomatous tube, or anal fistula, in the anorectal area. Perianal abscess is an abscess formed by infection in the soft tissues around the rectum and anal canal or in the interstitial space around it, also known as perianal abscess. Surgery is the preferred method of treating perianal abscesses, which mainly involves incising the abscess and draining the pus to eliminate it. However, as most of the abscess cavity of perianal abscess is connected to the anorectum, i.e., there is an internal opening. During surgical incision to drain the pus, the surgical incision, i.e., the external opening, the pus cavity will shrink and form a fistula after the operation, i.e., there will be an internal opening, fistula, and external opening in one tube, i.e., anal fistula. Because most of the perianal abscesses will form fistula after incision and drainage, so the surgery is often combined with the use of hanging thread, that is, after incision of the abscess to find the inner mouth, cut the skin and hang the thread, so that the abscess is completely open to avoid the formation of anal fistula. It is recommended that patients seek timely medical treatment, and the doctor will choose the appropriate surgical method to treat according to the specific situation.