Objective To investigate the influence of preoperative diabetes mellitus (DM) on postoperative morbidity of pancreatoduodenectomy for pancreatic ductal adenocarcinoma.Methods The clinical data of 302 pancreatic ductal adenocarcinoma patients who underwent pancreatoduodenectomy from January 1,2005 to August 31,2012 were retrospectively analyzed.Results 113 patients (37.4％)had preoperative DM among the total 302 patients.The percentage of the major complication including pancreatic fistulas,delayed gastric emptying,infections,acute kidney injury and mortality accounted for 19.9％,12.9％,25.9％,36.0％,3.2％ and 3.5％ respectively.In the DM group,firm pancreatic texture was more common than that in non-DM group (x2 =15.175,P ＜ 0.01).While pancreatic fistula in the DM group developed less frequently(x2 =7.811,P =0.005) than that in non-DM group.Delayed gastric emptying,infections,acute kidney injury,hemorrhage,pulmonary,cardiovascular and neurologic complications,as well as length of stay in hospital and mortality were in similar frequency in the two groups (P ＞ 0.05).Binary Logistic regression analysis showed DM(OR =0.358,P =0.035) and firm pancreatic texture(OR =0.395,P =0.032) were protective factors against pancreatic fistula while preoperative jaundice(OR =3.819,P =0.010) and intraoperative blood transfusion (OR =1.268,P =0.001) were predisposing factors for pancreatic fistula.Conclusions With good control of perioperative glucose level,DM does not increase operation risk in pancreatoduodenectomy for pancreatic ductal adenocarcinoma.