Abstract: ObjectiveTo provide evidence for exploring the mechanism of arsenic-induced hepatoxicity.MethodsForty mice were diveded into 4 groups,e.g.,one controls and 3 experimental groups(1 mg/L As₂O₃,2 mg/L As₂O₃ and 4 mg/L As₂O₃).As₂O₃ was administered for 60 days.Immunohistochemistry method was used to investigate 8-Nitroguanine expression in liver tissue of mice.ResultsExpression of 8-Nitroguanine was observed in the liver tissue of mice exposed to arsenic and there was relationship of dose-response in expression of 8-Nitroguanine with the increase arsenic dose.ConclusionArsenic induced high expression of 8-Nitroguanine in liver tissue of mice.8-Nitroguanine might be an earlier sensitive biomarker for arsenic toxicity to liver.