Abstract: The purpose of this study was to optimize the extraction of Ganoderma lucidum mycelium polysaccharides (GLP) derived from the mycelium of Ganoderma lucidum CZDG10 and to explore its antioxidant properties and protective effect on skin cell damage. The extraction of GLP was optimized using a combination of single factor experiments and the response surface method, with high-pressure crushing assistance and compound enzyme treatment. The antioxidant activity of GLP was analyzed, and the injury model of human skin fibroblasts (HSF) induced by H₂O₂ was evaluated to assess the efficacy of GLP in preventing cell damage. The optimal extraction conditions of GLP included a crushing pressure of 100 MPa, solid-liquid ratio of 1:40 g/mL, compound enzyme content of 2.40%, enzymatic temperature of 50.0 ℃, enzymatic pH of 5.5, and enzymatic reaction time of 2.25 h. Under these conditions, GLP was obtained in 9.69%±0.32% yield. GLP primarily comprised mannose, glucose, galactose, and fucose and effectively scavenged DPPH, OH, and ABTS^＋ free radicals, with IC₅₀ values of 0.30, 0.36, and 1.59 mg/mL, respectively, demonstrating its antioxidant capacity. Models of H₂O₂-induced HSF oxidative stress showed that GLP could improve the cell survival rate in a concentration-dependent manner and increase cell viability by 22.33% at a concentration of 1.0 mg/mL. GLP also up-regulated the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in HSF cells under oxidative stress induced by H₂O₂ and reduced the content of reactive oxygen species (ROS) and malondialdehyde (MDA), thereby reducing oxidative stress damage. In addition, GLP increased the content of collagen in HSF cells by reducing the matrix metalloproteinase-1 (MMP-1) content and promoting the secretion of collagen I in HSF cells, thereby maintaining the healthy state of the skin cells. Therefore, GLP exhibited a significant protective effect against H₂O₂-induced HSF cell damage. This study provides a theoretical basis for the development and application of polysaccharides from Ganoderma lucidum mycelium.