Objective To evaluate the impact of body mass index （BMI） on short-term outcomes after intersphi-ncteric resection （ISR） for rectal cancer and anal cancer. Methods One hundred and ninety-nine cases of rectal cancer and anal cancer who were treated in Department of Gastrointestinal Surgery of West China Hospital of Sichuan University from Jan. 2009 to Dec. 2011 were enrolled retrospectively，and these cases were divided into underweight group （n=23），normal group （n=114），and overweight group （n=62） according to BMI. Postoperative indexes in early rehabilitation and complication of 3 groups were studied and compared. Results On the recovery indexes after ISR in early stage，there were no significant differences on the duration of first flatus，first defecation，first oral intake，first ambulation，and hospital stay among 3 groups （P＞0.05）. On the tube management，there were no significant differences on the duration of pulling out nasogastric tube and urinary catheter （P＞0.05），but duration of pulling out drain was longer in normal group and over-weight group （P＜0.05）. There were no significant differences on the incidence of postoperative complications among the 3 groups （P＞0.05），including anastomotic leakage，anastomotic bleeding，perianal infection，ileus，gastric retention，urinary retention， septicemia，wound infection，and recto-vaginal fistula. Conclusions BMI has little impact on short-term outcomes after ISR. Obesity does not increase the incidence of common complications for patients after ISR and does not influence recovery indexes with proper postoperative managements.