Acute liver injury (ALI), which manifests as abnormal liver function and hepatocyte damage, lacks effective treatment modalities and is associated with a high mortality rate. Recent studies have revealed that hepatoprotection is related to polysaccharide components. In this study, we examined the effect and mechanism of Lycium ruthenicum Murray polysaccharides (LRMP) on liver injury induced by lipopolysaccharide (LPS). Male ICR mice were pre-administered LRMP (100 and 400 mg/kg BW) once daily for 21 days. A single injection of LPS (10 mg/kg BW) was administered on day 21 to induce ALI. The difference between the groups indicated that LRMP supplementation had no adverse effect on body weight. LRMP administration considerably alleviated liver injury, as evidenced by the decreased levels of aspartate transaminase and alanine transaminase, increased levels of albumin, and preservation of liver structural integrity. Moreover, LRMP reduced oxidative stress and inflammatory responses in the liver, maintained mitochondrial structure, regulated mitochondrial apoptotic pathway, and upregulated Sirtuin 1/peroxisome proliferator-activated receptor γ coactivator-1α signalling pathway involved in mitochondrial biogenesis. This study suggests the potential therapeutic application of LRMP in liver-related diseases, which will provide a basis for innovative strategies.