1. Trans-anal surgery: suitable for early rectal cancer within 5 cm from the anal verge; 2. Trans-posterior route surgery: suitable for early rectal cancer of 6-9 cm from the anal verge; 3. Trans-abdominal radical rectal cancer surgery: suitable for tumor lower margin distance greater than 7 cm from the anal verge (theoretically, this procedure requires the tumor lower margin to be at least greater than 5 cm from the anal verge (for early stage cancer), and for progressive stage cancer, the minimum distance should be greater than 6 cm); 4. Trans-anal Transanal sphincter rectal cancer resection and colorectal anastomosis: it is suitable for highly and moderately differentiated rectal cancer with the lower edge of tumor 2,5~5 cm from the anal verge, and this procedure is the ultimate procedure to preserve the anus, which can increase the anal preservation rate to 80%. 5. Transabdominal sacral radical rectal cancer surgery: it is suitable for primary rectal cancer whose lower edge of tumor is at a certain distance (6~8 cm) from the anal edge, but it is difficult to operate through the abdomen alone (if the safety of the lower incision line cannot be guaranteed).