Abstract: Objective: To study the oxidative injury induced by cypermethrin(CYP) in liver tissue of male mice.Methods: Forty Kunming male mice were randomly divided into the double steaming water lavage group(negative control group) and CYP at different dosage groups,the exposure dosages of CYP were 5,10 and 20 mg/kg respectively.CYP was administered to mice by gavage once daily for three weeks,then the liver index,the activities of glutathione peroxidase,catalase and total superoxide dismutase,the content of malondialdehyde in mice liver tissue were measured.Results: With the increase of CYP dosage,in the 5 mg/kg and 10 mg/kg CYP groups,the mice liver index was higher than that in the negative control group(P<0.01 and P<0.05);the activities of glutathione peroxidase in 10 mg/kg and 20 mg/kg CYP groups and catalase in the 20 mg/kg CYP group were decreased compared with the negative control group(P<0.01),the activities of superoxide dismutase were decreased in 5 mg/kg and 10 mg/kg CYP groups(P<0.01).Malondialdehyde content was increased in the 20 mg/kg CYP group compared with the negative control group(P<0.01).Conclusions: Cypermethrin can induce the oxidative damage in male mice liver tissue.