Objective:To research the significance of screening diabetes mellitus early,evaluate the insulin sensitivity and the function of secretion,and predict the development of diabetes and the complications,and provide early intervention for the patients. Methods:All the patients had oral glucose tolerance test(OGTT),and the body mass index(BMI) was calculated,and screening diabetes mellitus early and evaluation the sensitivity to insulin were performed. Results:The group of impaired glucose tolerance(IGT) patients,were younger than the group of diabetes mellitus(DM)(52.0±10.9 vs 65.1±14.3,P < 0.05). Compared with the group of normal glucose tolerance(NGT),the insulin sensitivity is decreased in the groups of impaired fasting glucose(IFG),IGT and DM,and insulin resistance was more obvious(NGT vs IGT:92.0±22.3 vs 64.7±13.1;NGT vs DM:92.0±22.3 vs 28.5±8.2. P < 0.05). Compared with the group of IFG,the insulin sensitivity of IGT decreased more. Compared with the group of IFG,the insulinogenic index(IGI) was higher in IGT(IFG vs IGT:1.69±0.80 vs 1.90±1.20,P < 0.05),and compared with the group of NGT,the early-phase insulin release(EPIR) was lower in IFG and DM(NGT vs IFG 1stPH:243.9±173.5 vs 124.2±110.2,2ndPH:99.2±33.5 vs 62.6±37.4;NGT vs DM 1stPH:243.9±173.5 vs 136.7±123.2,2ndPH:99.2±33.5 vs 38.8±33.3,P < 0.05),and 1stPH in IGT was higher than that in IFG(IFG vs IGT 1stPH:124.2±110.2 vs 200.4±186.32,P < 0.05). Conclusion:There are different pathogenesis in the patients of IFG and IGT,pancreas,β-cells are damaged in some patients of NGT,and OGTT has significant clinical meaning for revealing the function of pancreas β-cells, secretion and insulin resistance,and can direct screening,diagnosis and intervention for diabetes mellitus early.