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.