To evaluate the inhibition effect of Astragalus polysacharin (APS) on chemical hepatocyte injury of common carp,APS (0.2,0.4 and 0.8 mg/mL) was added to the primary hepatocytes pre-treatment,post-treatment and both pre- and post-treatment with the incubation of hepatocytes in the culture medium with 8 mmol/L CCl4.The morphology of liver cells was then observed by microscope,lactate dehydrogenase (LDH),glutamate pyruvate transaminase (GPT),glutamate oxalate transaminase (GOT),superoxide dismutase (SOD) and malondial-dehyde (MDA) in the supernatants were measured,hepatocyte viability was investigated and the mRNA expression of cytochrome P450 1A and 3A (CYP1A and CYP3A) in the hepatocytes were studied.The results showed that APS significantly improved cell viability,inhibited the elevation of GPT,GOT,LDH and MDA,and increased the SOD level in the supernatants (P＜0.05 or P＜0.01).The expression of CYP1A mRNA was improved in 0.4 and 0.8 mg/mL APS treatments (P＜0.05) and the expression of CYP3A mRNA was upgraded in 0.4 mg/mL APS treatment (P＜0.05).The observation of morphology also showed that APS effectively inhibited mortality of the hepatocytes.It can be concluded from the data obtained that APS exhibited protective effect against CCl4-induced hepatotoxicity in fish,and positively induced the expression of CYP1A and CYP3A.