Rectal cancer is one of the malignant tumors with the most number of surgical procedures, the most controversial and the most unstable prognosis among all bowel cancers. Rectum not only has a special location, but also a special structure and function. Part of the rectum is located in the pelvic cavity and part of it is located outside the pelvic cavity, connecting the anal canal and the anus, and responsible for the storage and excretion of feces. Therefore, rectal lesions are closely related to human defecation, which is the reason why many patients with low-grade rectal cancer require anal preservation rather than fistula, hoping to remove the tumor and defecate from the original anus at the same time.