ObjectiveTo evaluated the impact of obesity on surgical site infection (SSI)  following colorectal cancer surgery.MethodsA total of 215 patients undergoing radical surgery for colorectal cancer in a hospital between January 2008 and December 2013 were investigated retrospectively, 100 patients were with body mass index (BMI) ≥25 kg/ m2 (obesity group) and 115 patients with BMI＜25 kg/ m2 (normal weight group), the intraoperative and postoperative indicators and surgical complications were compared between two groups.ResultsIn obesity group, 72（72.00%） patients had intraoperative blood loss of ＞60 mL, 58（58.00%） patients’ duration of surgery was ＞220 min , 20 （20.00%）of whom developed postoperative SSI; in normal weight group, 30（26.09%） patients had intraoperative blood loss of ＞60 mL, 20（17.39%） patients’ duration of surgery was ＞220 min, 8（6.96%）of whom developed postoperative SSI. Intraoperative blood loss and  incidence of SSI in obesity group were both significantly higher than normal weight group, duration of surgery and postoperative length of hospital stay were both longer than normal weight group（both P<0.05）.ConclusionIncidence of SSI in colorectal cancer patients is high. Obesity, long duration of surgery, and more bleeding are high risk factors for SSI in colorectal cancer patients.