Objective：To compare the hepatic damaging effect in mice exposed to arsenic of different valence states (iAs3+ and iAs5+ ) and to probe into the related mechanisms.Methods: Sixty mice were divided into control group(distilled water),sodium arsenite group（iAs3+ ,300 mg/L）and sodium arsenate group（iAs5+ 300 mg/L）at random.The mice were sacrificed 10 months after exposure in the 3 groups.The liver function and total arsenic content in the liver were examined in each group.H-E staining and Masson staining were employed to observe the pathologic changes of the livers.Real-time RT-PCR were used to examine the expression of TNF-α,IL-6 ,GSH-Px,MMP-8,ColⅠand Col ⅢmRNA.Results: The accumulation of arsenic in iAs3+ group was higher than that in the iAs5+ group; the liver function of animals in iAs3+ group was worse than that in the iAs5+ group (P<0.05).H-E and Masson staining showed that the hepatic injury and fibrosis in iAs3+ group were severer than those in the iAs5+ group (P<0.05).The expression of TNF-α,IL-6,Col Ⅰand Col Ⅲ mRNA was higher and the expression of GSH-Px,MMP-8 mRNA was lower in arsenic exposed mice compared with those in the normal mice (P<0.05).Compared with iAs5+,animals in iAs3+ group had higher expression of TNF-α,IL-6,and Col ⅠmRNA (P<0.05).Conclusion: Long-term exposure to oral drinking with arsenic can result in hepatic injury and hepatic fibrosis by stimulating secretion of mediators of inflammation and ECM.And the effect of arsenic is related to the arsenic accumulation and the valence states of arsenic.