Abstract: The cis-emodin-emodin dianthrone (compound 1) and trans-emodin-emodin dianthrone (compound 2) were extracted from Polygonum multiflorum Thunb. The protective effect and mechanism of compound 1 and compound 2 (emodin-emodin dianthrones) on acute liver injury induced by concanavalin A (ConA) in ICR mice was first investigated. The results indicated that emodin-emodin dianthrones at 1 mg·kg^-1 significantly reduced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) level (P < 0.05). Emodin-emodin dianthrones also improved liver histopathological damage in liver-injured mice. The level of Bcl-2-associated X protein (Bax) mRNA in liver was significantly reduced by 1 mg·kg^-1 of emodin-emodin dianthrones, while the level of B-cell lymphoma-2 (Bcl-2) mRNA expression was significantly increased (P < 0.05). The protective activity of compounds 1 and 2 against hepatocyte injury was further evaluated by hydrogen peroxide (H₂O₂)-induced hepatocyte injury. Compounds 1 and 2 significantly inhibited H₂O₂-induced hepatocyte injury and reduced the levels of ALT, AST, alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) in cell culture. Compounds 1 and 2 also significantly improved the cell survival rate and decreased H₂O₂-induced oxidative stress in hepatocytes. Compound 1 (0.5 µmol·L^-1) significantly increased the enzymatic activity of superoxide dismutase (SOD) in hepatocytes (P < 0.01), and 0.5 µmol·L^-1 of compound 2 significantly decreased the intracellular reactive oxygen species (ROS), increased SOD enzyme activity, and glutathione (GSH) content (P < 0.01). Compounds 1 and 2 at 0.5 µmol·L^-1 also inhibited hepatocyte apoptosis by increasing the protein expression ratio of Bcl-2/Bax (P < 0.05) and decreasing the protein expression ratio of cleaved caspase-3 and pro caspase-3 (P < 0.05). This study indicates that the emodin-emodin dianthrones from Polygonum multiflorum Thunb. have liver-protective activity. Compounds 1 and 2 exerted hepatoprotective effects by inhibiting apoptosis and oxidative stress. The study provides an important material basis for the hepatoprotective effect of commonly used amounts of Polygonum multiflorum Thunb.