Objective To study the effect of lipid peroxidation and anti-lipid peroxidation and the pigment in skin of C57BL/6 mice exposed to arsenic.Methods Forty male C57BL/6 mice were divided into four groups via the random number table method,ten mice in each group,and the mice were fed ad libitum drinking water containing arsenic at 0,1,5 and 25 mg/L concentrations for a period of 6 weeks,respectively.Twelve days before the end of the experiment,procedure of depilation was performed to induce anagen of hair cycle.On the 30th day of experiment,the activity of superoxide dismutase (SOD) was determined by nitrite method,the activity of glutathione peroxidase (GSH-Px) was determined by dithiobisobenzoic acid method,the content of malondialdehyde (MDA) in skin of C57BL/6 mice was determined by thiobarbituric acid method.Melanin was measured by NaOH dissolution method.Results No significant difference was found in body weight and water intaken between groups (F =0.119,0.363,P ＞ 0.05).The activity of SOD [(16.00 ± 5.05),(13.96 ± 2.02),(10.46 ± 3.14) U/mg prot] in 1,5 and 25 mg/L arsenic groups were all significantly lower than that in control group [(20.36 ± 4.82) U/mg prot,P ＜ 0.05].GSH-Px activity in 1,5 and 25 mg/L arsenic groups [(98.14 ± 23.92),(87.18 ± 10.87),(53.56 ± 19.97) U/mg prot] were all significantly lower than that in control group [(119.34 ± 33.14) U/mg prot,P ＜ 0.05].While MDA levels in 5 and 25 mg/L arsenic groups [(9.09 ± 2.04),(11.48 ± 2.21) nmol/mg prot] were significantly higher than that of control group [(6.19 ± 0.56) nmol/mg prot,P ＜ 0.05] and that of 1 mg/L arsenic group [(6.52 ± 1.67) nmol/mg prot,P ＜ 0.05).No significant difference was found in melanin levels (P ＞ 0.05).Conclusions Lipid peroxidation and the decreasing of antioxidation may be one of the mechanisms of arsenic-induced skin damage.Arsenic-induced skin melanin content change is not found.