Abstract: Objective To observe the effects of sodium arsenic on cell proliferation,cell cycle and reactive oxygen species(ROS) production of human HaCaT cell.Methods HaCaT cells were exposed to sodium arsenic at the concentration of 0,25 and 50 μmol/L for 6 hours.Cells proliferation was measured by Alamar Blue assay,while cell cycle and ROS levels were measured by flow cytometry.Results Cell proliferations of 25 and 50 μmol/L groups(93.5%±1.18,82.9%±2.64) were significantly lower than that of control,but the ratio of G2/M phase cell (19.15%±0.29,18.12%±1.35) and ROS levels(128.61%±6.23,152.92%±7.25) of 25 and 50 μmol/L groups were significantly higher than those of control.Conclusion Sodium arsenic exposure could induce increased ROS production in human HaCaT cells,w hile the increasing of G2/M cell numbers induced by sodium arsenic exposure does not result from the proliferation of HaCaT cell.