Objective: To investigate the blood sugar lowering effects of different gastric bypass procedures in type 2 diabetic (T2DM) rats and the mechanisms involved. Methods: Fifty SD rats with T2DM induced by streptozotocin were equally randomized into 5 groups: Group A (sham operation control), group B (gastric bypass with exclusion of the duodenum), group C (gastric bypass with the exclusion of the proximal jejunum), group D (gastric bypass with the exclusion of the duodenum and proximal jejunum) and group E (gastrojejunal diversion without intestinal exclusion), respectively. The body weight gain and levels of fasting blood glucose (FBG), glucose-dependent insulin-releasing peptide (GIP) and glucagon-like peptide-1 (GLP-1) in rats of each group were determined before and 1 week, 3, 6 and 12 weeks after operation. Twelve weeks later, rats in group E underwent a second laparotomy to exclude the duodenum and proximal jejunum by occluding the duodenum distal to the gastric antrum, and the levels of FBG, GIP and GLP-1 were determined 1 week, 3 and 6 weeks after the second operation. Results: Compared with the preoperative values, the body weight of the rats in each group showed no obvious change one week after surgery (all P>0.05), which in group A, B and C still had no noticeable change 3 and 6 weeks after surgery (all P>0.05), but significantly increased 12 weeks after surgery and was most marked in group A (all P<0.05), but in group D and E were somewhat decreased 3 and 6 weeks after surgery (all P<0.05) and close to the preoperative levels 12 weeks after surgery (both P>0.05). The levels of FBG, GIP and GLP-1 in group A showed no obvious alterations at each postoperative time point compared with those before surgery (all P>0.05). The FBG levels decreased significantly and gradually from one week after surgery in group D, and decreased significantly and gradually from 3 weeks after surgery in group B, C and E (all P<0.05), which was most evident in group D and least in group E (all P<0.05), and had no difference between group B and C at the same time points after surgery (all P>0.05). The GIP values decreased significantly and gradually from one week after surgery in group B, C and D, which was most evident in group D (all P<0.05), and had no difference between group B and C at the same time points after surgery (all P>0.05). The GIP values showed no significant difference at each time point after surgery compared with preoperative value in group E. The GLP-1 values increased significantly and gradually from one week after surgery in group D and E, and increased significantly and gradually from 3 weeks after surgery in group B and C, which were significantly higher in group D and E than those in group B and C at the same time points after surgery (all P<0.05). Compared with the values before the second operation, the values of FBG and GIP significantly decreased (all P<0.05), while the GLP-1 values showed no significant differences (all P>0.05) in group E after the second operation. Conclusion: Gastric bypass with duodenal-jejunal exclusion has excellent blood glucose lowering effect in diabetic rats, and the mechanisms are associated with the low GIP secretion due to the food bypassing the duodenum and proximal jejunum, and high GLP-1 secretion due to the early and rapid passage of food into the distal jejunum and ileum.