Abstract: Excessive exercise makes the body consume more oxygen and produce excessive free radicals. The increased free radicals lead to oxidative stress injury and dysfunctions in liver tissue. Our previous study showed that Anwulignan, an active monomer in Schisandra sphenanthera Rehd. et Wils. (Schisandra), had anti-fatigue effects in mice. However, whether Anwulignan has a protective effect on liver damage in exhausted mice and the mechanism underlying remain elusive. An exhaustive swimming mice model was used to study the protective effects of Anwulignan on liver damage. The involvement of the nuclear factor (erythroid-derived 2)-like 2 (NRF2)/antioxidant responsive element (ARE) antioxidative pathway in Anwulignan-mediated anti-fatigue was analyzed using NRF2 inhibitor ML385 in HepG2 cells treated with H₂O₂. Animal welfare and experimental process follow the regulations of the Animal Ethics Committee of Beihua University. Anwulignan significantly lowered serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, reduced liver tissue damages, increased superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), and decreased malondialdehyde (MDA) and 8-hydroxy-2 deoxyguanosine (8-OHdG) contents in the livers of exhausted mice, demonstrating a strong antioxidant effect. Furthermore, Anwulignan up-regulated the NRF2/ARE antioxidant pathway in liver tissue, increased B-cell lymphoma 2 (Bcl-2) expression, and decreased Bcl-2-like protein 4 (Bax) and caspase3 expression. In HepG2 cells, Anwulignan improved the cell viability and SOD activity, reduced reactive oxygen species (ROS) and MDA contents, up-regulated the expression of the NRF2/ARE signaling pathway and Bcl-2, and decreased Bax and caspase3 expression in the cells. Furthermore, pretreated ML385 partly abolished all these effects of Anwulignan. Anwulignan protects the liver from damage in the exhausted mice by its antioxidant effects and related to its activation of the NRF2 pathway.