OBJECTIVE：To study the hepatotoxicity of main components of Polygonum multiflorum ，and investigate its toxic mechanism based on metabolic enzymes. METHODS ：ADMETlab 2.0 platform was used to forecast the toxic or carcinogenic effects of emodin ，physcion，rhein，stilbene glycoside and gallic acid on liver ，skin and heart. The effects of those components on cytochrome P 450 enzyme system （CYP1A2，CYP2C9，CYP2C19，CYP2D6，CYP3A4）were evaluated. The effects of different concentrations of emodin ，rhein，stilbene glycoside and gallic acid （10，20，40，80 μmol/L）on the survival rate of normal hepatocyte L 02 were detected. The effects of major components of P. multiflorum on the activity of UGT 1A1 enzyme were studied by in vitro reaction system ，using bilirubin as substrate. RESULTS ：Main components of P. multiflorum ，ie. emodin ，physcion， rhein and gallic acid ，showed strong toxic effects on the liver ，while stilbene glycosides possessed weak toxic effects on the liver. Emodin and physcion had strong inhibitory effects on CYP 1A2 and medium inhibitory effects on CYP 2C9，CYP2D6 and CYP3A4；rhein showed medium inhibitory effects on CYP 1A2 and CYP 2C9，while stilbene glycoside and gallic acid possessed weak inhibitory effects on the above enzymes. Emodin （40，80 μmol/L）and gallic acid （40，80 μmol/L）could significantly reduce the survival rate of L 02 cells（P＜0.01）. The inhibition rate of 5，10，20，40，80 μmol/L emodin and gallic acid（except for 5 μmol/L emodin）on UGT 1A1 enzyme increased significantly （P＜0.01），and the inhibition effect of emodin on UGT 1A1 enzyme was reversible competitive inhibition. CONCLUSIONS ：The main components of P. multiflorum ，ie. emodin ，rhein and physcion ， are hepatotoxic ；the mechanism of it may be associated with inhibiting the activity of CYP 1A2 and CYP 2C9 and competitively blocking rate-limiting enzyme UGT 1A1 in the process of bilirubin metabolism.