Objective:To evaluate the effect of gastric bypass on  fasting blood glucose levels in  Goto-Kakizaki(GK) rats. 
Methods:Thirty-two GK  type 2 diabetic rats were devided into four groups with different fasting blood glucose level: Group A,（<10 mmol/L）;Group B,（10~15 mmol/L）; Group C,（15~20 mmol/L）; Group D,（>20 mmol/L）.Rats were observed for 24 weeks after gastric bypass(GBP) surgery. Fasting blood glucose level and fasting insulin level were measured at 0, 1, 3, 6, 12 and  24 wks postoperatively.  The 24-week descend ratio of glucose after operation was calculated by formula.
Results:The glucose descend ratio of each groups was 35.4%, 44.3%, 40.3% and 30.1%, respectively. But, campared to pre-operation, the insulin level of all groups showed no significant change (P>0.05).
Conclusions: In spontaneous type 2 diabetes mellitus rats, gastric bypass operation was effective in all the groups in terms of glucose control. But the effect on glucose control varied among the groups. These findings suggest that there is more marked effect when the preoperative fasting blood glucose level between 10  mmol/L and 20 mmol/L.