Objective The present study is designed to examine the responses of human osteosarcoma MG63 cells to hyperhomocysteinemia(HHcy) and the possible mechanisms. Methods MG63 cells were cultured in DMEM contain 10% fetal bovine serum at 37℃ with a humidified atmosphere 5%COSUB>2/SUB>.They were treated in different concentration and different time by HHcy. MG63 cells were used as EM>in vitro/EM> model to assess the cell intracellular reactive oxygen species (ROS) that was evaluated by the fluorescence probe 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA). The cell apoptosis was observed by means of Hoechst/PI nuclear staining and fluorescence microscopy. The expressions of apoptosis-related protein Caspase-3 and Bax were analyzed with Western blotting. Results After MG63 cells were treated with HHcy in different concentrations and for different time. HHcy induced the cell death through accumulation of intracellular ROS in a dose-and time-dependent manner, at the same time activation of Caspase-3 and upregulation of Bax apoptosis-related protein. Conclusion HHcy exerts apoptosis-inducing effects on human osteosarcoma MG63 cells through accumulation of intracellular ROS and activati