Conclusion For patients with low REC，related risk factors of sphincter-preserving operation include infiltration depth，differentiated degree，distance of anal verge and infiltration perimeter，and infiltration depth，differentiated degree and distance of anal verge are independent risk factors of sphincter-preserving operation.It is of great importance to chose operation plans in improving patient’s long-term survival rate and in preventing local recurrence rate according to above-mentioned factors.In addition ......