Abstract: Objective To explore the effect of sodium arsenite(NaAsO₂)on antioxidative ability in human keratinocytes(HaCaT).Methods The fluo rescence in tensity of dichlorofluoresce in(DCF)was detected by flow cytometry.The malondia ldehyde(MDA)content was detected by improved thio-barbituric acid fluorometric method.Superoxide dismutase (SOD)activity was dete rmined by Nitrite-kit.The catalase(CAT)activity was determined by ultraviolet velocity direct method.Results The fluorescence in tensity of DCF increased to 1.3,1.6,1.7,and 1.8 times of the control's in 215,10,and 20μmol/L NaAsO₂ treated groups,respectively(P<0.05).The MDA content increased to 1.1,1.4,1.5,and 2.2 time of the control's in 215,10,and 20μm o l/L NaAsO₂ treated groups,respectively(P<0.05).While the activity of SOD decreased to 78% and 61% of the control's in 10μmol/L and 20μmol/L NaAsO₂ groups.And CAT activity decreased to 50% and 34% of the control's in 10μmol/L and 20μmol/L NaAsO₂ groups.Conclusion A rsenic can cause oxidative damage and decrease antioxidative ability in human keratinocytes.