Abstract: Objective: To investigate the oxidative stress condition in patients with different impaired glucose regulation and analyze the relevance of oxidative stress and insulin resistance(IR) and -cell function. Methods: Twenty-eight patients with normal glucose tolerance(NGT) , 30 with impaired fasting glucose(IFG) , 30 with impaired glucose tolerance(IGT) and 32 with type 2 diabetes mellitus (T2DM) were observed. The serum SOD,GSH-PX and MDA levels in all cases were measured,with HOMA-IR,HOMA-,I30 / G30,MBCI respectively to assess IR, the basal insulin secretion, early stage of insulin secretion and insulin secretion after glucose load. Results: Compared to NGT, the serum MDA level was increased from NGT、IFG、IGT toT2DM(P ＜ 0. 01) . Compared to IFG, there was statistical difference in IGT and T2DM(P ＜ 0. 01) . There was no statistical difference between IGT and T2DM(P ＞ 0. 05) . The serum SOD,GSH-PX levels were decreased from NGT, IFG, IGT to T2DM. There was statistical difference between NGT and T2DM and no statistical difference among IFG,IGT and T2DM. There was positive correlation between MDA and HOMA-IR,between SOD and HOMA-,△I30 /△G30,MBCI,between GSH-PX and HOMA-,MBCI. There was negative correlation between MDA and HOMA-, △I30 /△G30,MBCI,between SOD and HOMA-IR. Conclusions: IR and -cell function decline was important pathophysiological changes in type 2 diabetes mellitus and emerged before the diagnosis of diabetes. From NGT、IFG、IGT to T2DM, the degree of oxidative stress was getting higher and oxidative injury was existed in pre-diabetes mellitus. There was confidential correlation between oxidative stress and IR and -cell function. Oxidative stress may have an important function with the development of T2DM.