Objective To observe the hypoglycemic effect and influence on islands of langerhans of gastric bypass operation in type 2 diabetes rats.Methods Healthy male SD rats were randomly divided into type 2 diabetes-operation group (DO group),type 2 diabetes-sham operation group (DS group),type 2 diabetes-control group (DC group) and normal-operation group (NO group) (n =8 each).Plasma glucose concentration and insulin levels were measured respectively at fasting condition before,and 1 week,2 weeks,4 weeks and 8 weeks after operation.Pancreas pathological changes were observed two months after gastric bypass operation.Results The fasting blood glucose concentrations in DO group at the second week postoperation was decreased from (17.80 ± 2.26) to (14.93 ± 1.78) mmol/L (P ＜ 0.05),and those at 8th week postoperation decreased to (6.18 ±0.53) mmol/L (P ＜0.05).The fasting blood glucose concentration in DO group was significantly lower than in DS and DC groups postoperation (P ＜ 0.05).The fasting plasma insulin levels in DO group were increased from preoperative (11.89 ± 0.87) to (14.70 ± 1.04) mmol/L (P ＜ 0.05) at 8th week after gastric bypass operation.Postoperative pathologic examination revealed that average islands of langerhans in DO group were increased significantly as compared with DC and DS groups (P ＜ 0.05).In DO group,the islands of langerhans were obviously big,and the islet cells density increased.Conclusion Gastric bypass operation can markedly reduce plasma glucose concentrations in type 2 diabetes rats and increase fasting plasma insulin levels,which might be contributed to the increases in islands of langerhans after gastric bypass operation.