Objective：To investigate protective effect and mechanism of procyanidin in acute liver injury induced by acetaminophen. Method：The KM mice were randomly divided into six groups（n=8），including PBS control group，acetaminophen model group，pro－cyanidin control group（100 mg/kg） and procyanidin pre-treatment groups including low-dose（10 mg/kg），medium-dose（50 mg/kg） and high-dose groups（100 mg/kg）. The activities of alanine aminotransferase（ALT），aspartate aminotransferase（AST），malondialde－hyde（MDA） in the serum and the concentration of MDA in the liver homogenate of the mice were detected by commercial kits. Mean－while，the pathological changes of the liver were observed by HE staining，and the expression of SOD was determined by Western blot. Results：Compared with those in APAP model group，ALT（F=555.20，P=0.000），AST（F=168.51，P=0.000），MDA（F=155.15，P=0.000） in pre-treatment groups of medium-dose and high-dose of procyanidin were significantly lower，while SOD（F=291.84，P=0.000） was markedly higher. The damaged liver structure，hydropic degeneration and the central venous congestion were observed in the APAP model group，but the liver injuries in pre-treatment groups of medium-dose and high-dose of procyanidin were slighter. Based on the results of Western blot，SOD protein expression in APAP model group was inhibited，while the pre-treatment with medium-dose and high-dose of procyanidin could rescue its expression. Conclusion：Procyanidin has a protective role in acetaminophen-induced acute liver injury，and the preliminary mechanism is related to antioxidative character of drug.