Objective　To provide the guidance for transanal rectal resection through anatomic observation with the center of lower rectum.　Methods　The rectal adjacent structures were observed and the width and thickness of anus sphincter were measured, and then the thickness of recto-vaginal gap and recto-urethra gap were measured and recorded on 14 basin specimens and the film of basin CT scan in 28 adults which were selected from the material without pelvic diseases. The data were compared among different measuring ways and sexes and analyzed with t-Test statistically.　Results　There were many muscular structures surrounded the lower rectum and anus, and every muscule with fascia bandle itself could be recognized easily. The measured values of recto-urethra gap on basin specimens and CT films were（1.65±0.19）cm and （1.26±0.05）cm ,and the values of recto-vaginal gap were（0.89±0.11）cm and（0.75±0.04）cm respectively. It was larger in basin specimens than that in CT films and also larger the values of recto-urethra gap in males than that of recto-vaginal gap in females with significant statistical differences (P< 0.05).　Conclusions　Recognition the structures carefully and keeping the anatomic plane are necessary for avoiding invase injury, because of complicated adjacent structure around the lower rectum and thining recto-vaginal septum.