Laparoscopic surgery for rectal cancer has been successfully proven to be a non-inferior alternative regarding resection quality, and oncological outcomes of patients as compared to open surgery in mangy clinical trails. Moreover, laparoscopic surgery is advantageous over open surgery with regard to operative invasiveness, patient's recovery, and wound related complications. Thus, laparoscopic surgery has gained great popularity over the past decades. However, specifically for mid and low rectal cancer, laparoscopic surgery is technically demanding, which sometimes leads to high morbidity and unsatisfactory resection quality, especially in challenging cases such as bulky mesorectum, enlarged prostate, irradiated pelvis, etc. Under this circumstance, transanal total mesorectal excision (TaTME) , the so called down-to-up alternative, has emerged as a promising solution to these problems in recent years and more and more small studies have proven the feasibility and advantages of this technique, making it become a hot topic among both literature and conferences. However, TaTME is still at early birth, higher-level evidences, either multicentric, or comparative study with conventional surgery is strikingly lacking. Thus the investigators conduct this multicentre randomised clinical trial, comparing transanal TME versus laparoscopic TME for mid and low rectal cancer, aiming to prove the hypothesis that TaTME may achieve better resection quality and result in non-inferior oncological outcome, as well as short term operative morbidity and mortality.