Abstract: Objective To study protective effect of tert-butylhydroquinone in HaCaT cells on the damage induced by NaAsO₂ in vitro.Methods Alamar Blue reduction rate was used to evaluate cell vitality.The level of reactive oxygen species(ROS)was detected by staining cells with 2',7'-dichlorofluorescin diacetate(DCFH-DA).The melondiadehyde(MDA)level was measured by thiobarbituric acid(TBA)method.Results The viability of HaCaT cells was decreased by 82% and 59% after exposed to NaAsO₂ at the concentrations of 25 μmol/L and 50 μmol/L but the viability was 92% and 91% for the two exposure groups pretreated wtih tert-butylhydorquinone(tBHQ).Comparted to the control groups,the level of ROS increased by 1.64 and 3.86 times in the HaCaT cells exposed to 25 μmol/L and 50 μmol/L NaAsO₂ but only by 0.95 and 1.87 times for the same exposure groups pretreated with 25 μmol/L tBHQ and by 0.79 and 1.69 times for the two groups pretreated with 50 μmol/L tBHQ.The MDA levels increased significantly in HaCaT cells exposed to NaAsO₂(2.28 mol/L/mg·prot for 25 μmol/L NaAsO₂ exposure,2.96 mol/L/mg·prot for 50 μmol/LNaAsO₂ exposure; P < 0.01)and the increased levels of MDA were 2.05 μmol/L/mg·prot and 2.43 mol/L/mg·prot for 25 μmol/L pretreatment of tBHQ and 2.10 nmol/mg · prot and 260 nmol/mg · prot for 50 μmol/L/L tBHQ pretreatment groups.Conclusion tBHQ could protect HaCaT cells from damage induced by NaAsO₂ in a dose-reaction manner.