RATIONALE: Colorectal cancer is one of the most common cancers. However, approaches to minimize surgical trauma, preserve anal function, avoid abdominal stoma, and improve quality of life for patients with ultralow rectal cancers were limited. Thus, new technologies are urgently needed to improve the anal preservation rate, reduce the incidence of anastomotic leakage and improve postoperative anal function in patients with ultralow rectal cancer. PURPOSE: This one-arm multicenter prospective cohort study aims to collect the data of patients with ultralow rectal cancer who undergo sphincter-preserving surgeries, including modified PPS and conventional surgeries, then compare the effects of different operations on clinical outcomes and to see the efficacy and safety of modified PPS surgery when compared with conventional procedures in the treatment of ultralow rectal cancer.