Transanal total mesorectal excision (TaTME) is a novel development in the field of colorectal surgery which combines the mini-invasive concept of natural orifice transluminal endoscopic surgery(NOTES), the technique of single-port laparoscopic surgery and the principle of total mesorectal excision with curative intent for treating rectal cancer. Based on the platform of either transanal endoscopic microsurgery(TEM) or transanal minimally invasive surgery (TAMIS), it is an innovative way of retrograde TME dissection from bottom to up with or without laparoscopic assistance. It is supposed to facilitate distal rectal mobilization, thus achieving precise and sufficient distal margin and to reduced need for multiple stapler firings in transecting the rectum, consequently decreasing anastomotic leakage rates which is especially important for obese male patients with a narrow pelvis where exposure to the distal rectum from the abdominal approach can prove difficult. It could also protect neurovascular bundle with better visualization and exposure and has the advantage of better function and avoiding sacrificing sphincter. After a series of preclinical trail of animal and cadaver, it has been successfully applied to humans and successional reports have proved its feasibility and safety. However, the majority of published series is hybrid NOTES, which need the assistance of conventional laparoscopic surgery from above to bottom and abdominal incision, scar, pain and incision related complications such as wound infection, abscess, hernia and implanted incisional tumors cannot be necessary avoided. It is also worried that the cost will increased since two groups of surgical equipment are needed(the abdominal and perineal) and more surgical staff are required if the two team operate at the same time(two-team approach). Up to date, as far as we have known, the pure transanal TME NOTES without any laparoscopic assistance has also been successfully performed in human patients though the cases are rare. The investigators of our center have also successfully performed pure-NOTES rectal resection in human cadavers in the past few months, and are confident to move this forward to conduct this pilot study to evaluate the feasibility and safety of this surgery in rectal cancer patients.