Objective To investigate the changes of glucagon-like peptide-1 (GLP-1) in plasma and GLP-1 receptor (GLP-1 R) in pancreas after gastric bypass in rats with type 2 diabetes mellitus (GK rats) and to discuss the antidiabetic mechanisms.Methods Thirty male GK rats aged 8 weeks were randomly divided into 3 groups:the operation group (n =10),the sham operation group (n =10) and the diet pairing group (n =10),and 10 male SD rats aged 8 weeks served as blank control group (n =10).The levels of fasting blood glucose (FPG) and GLP-1 were measured and compared among the 4 groups at 1st,2nd and 4th week after the operation,and then the rats were decapitated to retrieve the pancreas to hematoxylin and eosin (HE) staining.Histomorphological changes including single islet area and pancreas islet number in each group were observed after HE staining under light microscopy,and the changes of GLP-1R expression were measured by immunohistochemistry.Results In GK operation group,the FPG levels [(11.06 ±0.52),(7.49 ±0.34),and (5.20 ±0.08) mmol/L] were decreased to the normal from the 1 st week after the operation (P ＜ 0.05),and the GLP-1 levels [(12.11 ± 0.40),(13.64 ± 0.23),and (26.40 ± 0.39) pmol/L] increased significantly (P ＜0.01).The size of single pancreas islet and the amount of pancreas islets were increased significantly,and the expression of GLP-1R in the pancreas was significantly higher in GK operation group.Conclusion Gastric bypass surgery can significantly reduce the blood glucose level.The up-regulation of GLP-1 and GLP-1R expression was one of the important mechanisms regulating blood glucose.