Inclusion Criteria:  Pathologically diagnosed as rectal cancer with the lower margin of the tumor from the anal margin ≤5cm；CT, MRI or endoscopic ultrasonography: Single tumor, clinical T stage ≤3 or no invasion of the internal sphincter, maximum diameter ≤10cm, no distant metastasis；The patient or the patient-authorized representative completely understands the study protocol and voluntarily participates in this study, agrees to sign written informed consent.  Exclusion Criteria:  The patient had previous abdominal surgery that will significantly infect the laparoscopic procedures; Patients requiring emergency surgery owing to intestinal obstruction, perforation, or uncontrolled bleeding caused by tumor; Patients with poor anal function preoperatively (Wexner score ≥10); ASA (American Society of Anesthesiologists) grading ≥ IV; Pregnant patients; Patients concomitant with severe mental illness; The patient or the patient-authorized representative can't understand the contents and objectives of the study.  Withdraw criteria： ISR cannot be performed by intraoperative evaluation and is replaced by Miles surgery; Distant metastasis is confirmed intraoperatively or by postoperative pathological findings; Patients had other primary tumors requiring surgical/drug treatment during the study, or had other illnesses that prevent the patient from continuing to participate this study; Patients decide to withdraw from the study for any reason, or who are unable to complete the study because of any objective reasons.