Carbon tetrachloride(CCl₄)has been widely used as a kind of classic liver poison in constructing mammalian liver injury model and screening liver protecting drug.To investigate toxicity effects of CCl₄ on hepatocyte DNA of Cyprinus carpio var.Jian,the alkaline single-cell gel electrophoresis(comet assay),histopathological examination of liver and the measuring of biomarkers of hepatocyte damage were performed respectively after low,middle and high concentrations(6.25% and 12.50% and 15.00% CCl₄ in olive oil,v/v)of CCl₄ at a volume of 0.01 mL/g of body weight being injected intraperitoneally into C.carpio var.Jian for 72 h.Meanwhile,the Real-time PCR was carried out to elevate the effects of CCl₄ on CYP3A mRNA expression.Results showed that the group injected with 6.25% of CCl₄ for 72 h has no obvious change(P>0.05)on histopathological examination,serum hepatase activities and mRNA expression of CYP3A,compared to the control,however,the comet assay results of hepatic cells showed that tail length,tail DNA(%),tail moment and olive tail moment increased significantly(P＜0.01).With the increase of concentrations,histological changes such as cell swelling,extensive vacuoles degeneration,karyopyknosis and karyolysis were observed.The groups injected with 12.5% and 15% of CCl₄ could significantly elevate the serum levels of glutamate oxalate transaminase(GOT)and glutamate pyruvate transaminase(GPT)(P<0.01 or P<0.05),and the group with 15.00% of CCl₄ produced a significant effect in the case of lactate dehydrogenas(LDH)and malondialdehyde(MDA)(P<0.05).All damage indexes of comet assay also increased with the increase of CCl₄ concentrations(P<0.01).At the same time,the expressions of CYP3A of the groups injected with 12.5% and 15% of CCl₄ were significantly reduced(P<0.05).Overall results proved the toxicity effects of CCl₄ on hepatocyte DNA of C.carpio var.Jian.Within the range of experimental concentrations,CCl₄ could inhibit CYP3A mRNA expression.And the results of serum hepatase activities,histopathological examination and comet assay were observed not only in a dose-dependent manner but also having good coherence with the increase of CCl₄ concentrations.The technique of comet assay showed higherr sensitivity.