Objective:To investigate the function of oxidative stress in apoptosis and proliferation of MC3T3-E1 cells under high glucose. Methods:MC3T3-E1 cells cultured in vitro were divided into normal control group,N-acetyl-L-cysteine(NAC) group,11.0 mmol/L high-glucose group,11.0 mmol/L high-glucose+NAC group,22.0 mmol/L high-glucose group and 22.0 mmol/L high-glucose+NAC group. Reactive oxygen species(ROS) production was measured with DCFH-DA fluorescent probe. Cell proliferation was mea-sured by MTT analysis. Cells in different groups were stained with Annexin V-FITC/PI,then the apoptosis rates were detected by flow cytometry. Morphology of cell nucleus was observed with Honchest33258. Results:①Cell apoptosis of 11.0 mmol/L high-glucose in-creased dramatically compared with that of normal control group(P=0.004). Cell apoptosis in 22.0 mmol/L high-glucose group in-creased significantly compared with that of normal control group and 11.0 mmol/L high-glucose group(P=0.000;P=0.000). ②Prolif-eration in 11.0 mmol/L high-glucose slightly decreased compared with that of normal control group(P=0.305). Compared with that of normal control and 11.0 mmol/L high-glucose group,proliferation in 22.0 mmol/L high-glucose group decreased significantly(P=0.001;P=0.009). ③ROS production in osteoblasts remarkablely increased under high glucose(P=0.000;P=0.000),but not in a dose-dependent manner. NAC,as an antioxidant,could reduce ROS production obviously and ameliorate cell apoptosis and proliferation abnormality caused by high glucose. Conclusion:High glucose can increase ROS production in osteoblasts and subsequently lead to the increase of apoptosis and decrease of proliferation.