Cancer of the anus, that is, cancer of the anal canal and perianal area, is called cancer of the anal canal, and cancer of the perianal area with a diameter of 5cm centered on the anus is called cancer of the perianal area. Perianal and anal canal cancers are most common in squamous epithelial cell carcinoma, and the causes are related to chronic inflammatory stimulation in the perianal area, viral infection, smoking, anal sex and the use of immunosuppressive drugs. It can be manifested as persistent pain in perianal area, a small amount of blood in stool in early stage, accompanied by foreign body sensation in anus and increased frequency of bowel movement. Irregular lumps with pressure pain can be touched by anal diagnosis, and pathological and histological examination can make a clear diagnosis. Some patients treat blood in stool caused by anal cancer as hemorrhoids and delay diagnosis, which needs to be taken seriously. Once there is unexplained blood in stool and change of bowel habit, it is necessary to go to the hospital in time for examination, to clarify the specific cause of the disease, and to give treatment as soon as possible.