Abstract： Objective To investigate the effects of 2-methoxyestradiol( 2-ME) on apoptosis of K562 cells and its mechanisms. Methods The K562 cells were cultured and divided into three groups. The control group: K562 cells were cultured without 2-ME treatment. The experimental group: K562 cells were cultured in the medium containing different concentrations of 2-ME (1, 2, 4, 8 and 16 μmol/L) for 36 h. The negative control group: K562 cells were replaced by water without RNase in the medium containing different concentrations of 2-ME for 36 h. The apoptosis rate, the protein and its mRNA expression of Caspase-3 and XIAP, the activity of superoxide dismutase (SOD) and reactive oxygen species (ROS) of K562 cells wasdetected by TUNEL, flow cytometry (FCM), half-quantitative RT-PCR and xanthenes oxidized enzyme assay,respectively. Results After treated with 2-ME at different concentrations for 36 hours, in the specified concentration range, 2-ME induced apoptosis of K562 cells in a concentration-dependent manner. The possible functional mechanism of 2-ME was to up-regulate Caspase-3 but down-regulate XIAP mRNA expression, and increase ROS activity but decrease SOD activity. Conclusion 2-ME can induce apoptosis of K562 cells in a concentration-dependent manner and indicate its promising potential in the treatment of chronic myeloid leukemia(CML) patients.