In the early stage of work, the investigators performed preservation of Denovilliers' fascia in L-PANP-TME to discuss the protection of urinary and sexual function of male mid-low rectal cancer patients. The results showed that preservation of Denovilliers' fascia in L-PANP-TME significantly decreased incidence of urinary and sexual function disorder. In order to further confirm the early work, the investigators design a randomized controlled clinical trial to compare differences in urinary and sexual function protection and long-term outcomes between preservation and excision of Denovilliers' fascia in L-PANP-TME.