Objective To investigate the characteristics of glycemic excursion of different subtypes of glucose tolerance. Methods Assessed by oral glucose tolerance test (OGTT) repeated twice, 81 individuals were divided into 4 groups: normal glucose tolerance (NGT, n=18), isolated impaired fasting glycemia (IFG, n=12), isolated impaired glucose tolerance (IGT, n=19), combined IFG/IGT (n=11), and newly diagnosed type 2 diabetes mellitus (T2DM, n=21). And then continuous glucose monitoring system (CGMS) was used for 72 hours to monitor the blood glucose (BG) level before drug intervention. Results (1) The levels of largest amplitude of glycemic excursions (LAGE), mean blood glucose (MBG), and standard deviation of mean level of blood glucose fluctuation (SDBG) increased gradually with the deterioration of glucose tolerance. The mean amplitude of glucose excursion (MAGE) readout of the IGT group was (3.2±1.2) mmol/L , significantly higher than that of the NGT group [(1.6±0.5) mmol/L, P<0.05], and significantly lower than that of the T2DM group [(5.2±1.9) mmol/L, P<0.05]. The level of frequency of glucose excursion (FGE) decreased along with the decrease of glucose tolerance: NGT group [(6.1±3.4)] > IGT/IFG group [(5.5±2.5)] > T2DM group [(4. 8±1.8)]. Among the three components of IGR, the IGT group showed highest MAGE (3.2±1.2) mmol/L and lowest FGE level (4.9±1.8). (2) The level of absolute mean of daily difference (MODD) increased in the following order: NGT group [(0.8±0.3) mmol/L], IGT group [(1.1±0.4) mmol/L], IFG/IGT group [(1.2±0.4) mmol/L], and T2DM group [(2.0±1.0) mmol/L] (all P<0.05). (3) The fasting glucose level deteriorated the most rapidly in the IFG group, while it reached the highest postprandial peak in the IFG/IGT group. The blood glucose curve increased along the order of NGT, I-IGT, IFG/IGT, IFG, and T2DM. (4) When the level of glycosylated hemoglobin (HbAlc) level was less than 7%, the fasting phase of curve virtually coincided with each other among individual groups with different HbAlc levels; however, the postprandial peak separated slightly. When the HbAlC level was between 7. 0% and 7.9% , the postprandial peaks of individual groups with different HbAlc levels dispersed markedly. When the HbAlc level was higher than 8% , the fasting blood glucose curve moved upwards significantly with increasing postprandial excursion. Conclusion (1) With the deterioration of glucose regulation, the intraday and day-to-day blood glucose excursions become increasingly fluctuant. (2) The amplitude of glycemic excursion is lower in the NGT group than in the T2DM group, however, the frequency of glycemic excursion is higher in the NGT subject than in the T2DM subjects. The glucose excursion profile of the IGR subjects is between the NGR and T2DM subjects. (3) The characteristics of glucose excursion of the IGT group are similar to those of the T2DM group, and the characteristics of the IFG group are similar to those of the NGT group. (4)The loss of postprandial glycemie control precedes evident deterioration in fasting phase of IGR.