Abstract: Objective To study the effect of leucine on blood glucose and its mechanism. Methods Forty-five Kunming mice were divided into low-leucine group,high-leucine group,and control group（15 in each group）.Mice in low-leucine group were orally given a mixture of leucine（0.7g/kg） and glucose（2.0g/kg）,those in high-leucine group were orally given a mixture of leucine（2.0g/kg） and glucose（2.0g/kg）,and those in control group were orally given glucose（2.0g/kg） only.Blood glucose level was measured at 0.5,1 and 2h,respectively,after ingestion of leucine and glucose.Glucose tolerance was tested after oral intake of starch to exclude the influence of oral intake of leucine on glucose absorption in the gastrointestinal tract.Blood glucose level was measured at 0.5,1 and 2h after ingestion of leucine and starch.In another experiment,mice were killed at 0.5 after oral administration of glucose and leucine.Blood insulin and glucagon like peptides-1（GLP-1） levels were measured by ELISA. Results The levels of blood glucose at 0.5h and 1h after oral intake of leucine,glucose and AUC were significantly lower in low-leucine group and in high-leucine group than those in control group,respectively.The levels of blood glucose at 0.5h after oral intake of leucine,glucose and AUC were significantly lower in high-leucine group than those in low-leucine group;The levels of blood glucose at 0.5h,1h and 2h after oral intake of leucine,starch and AUC were significantly lower than those in control group;The concentration of insulin and GLP-1 increased significantly in high-leucine group than those in control group,but no significant changes were noted between low-leucine and control group. Conclusion Leucine decreased blood glucose by increasing insulin and GLP-1 secretion.