Abstract: Polysaccharides are one of the key bioactive components of Grifola frondosa (GF). This study aimed to optimize the extraction process of Grifola frondosa polysaccharide (GFP) and evaluate its antioxidant, tyrosinase inhibition, and lipid-lowering activities. After pretreatment of GF fruiting bodies with ethanol, the GFP was isolated by low-temperature ultrasound-assisted compound enzymatic extraction. The optimal extraction conditions were determined as follows: solid-liquid ratio of 1:30 (g/mL), enzymatic pH of 7.0, enzymatic duration of 100 minutes, enzymatic temperature of 60℃, and ultrasonic power of 400 W. Under these conditions, the yield of GFP was 26.37%± 0.49%. The results showed that GFP's antioxidant activity was concentration-dependent. When the concentration was 3.0 mg/mL, the scavenging rates against DPPH free radicals, hydroxyl free radicals, superoxide anion (O₂^-), and ABTS free radicals were 78%, 55%, 80%, and 60%, respectively. Moreover, its total reducing power showed an absorbance value of 0.54 at 3.0 mg/mL, indicating a significant electron-donating ability. Furthermore, GFP inhibited oleic acid-induced lipid accumulation in HepG2 cells. Treatment with 100 μg/mL of GFP for 24 hours decreased intracellular triglyceride (TG) and total cholesterol (TC) levels by 35.6% and 31.7%, respectively. Western blot analysis revealed that a high concentration of GFP upregulated PPARγ and p-FOXO1 protein levels, while downregulating G6Pase expression. This study optimized an efficient green extraction process for GFP and discovered its tyrosinase inhibition activity. At a mass concentration of 3.0 mg/mL, GFP exhibited a tyrosinase inhibition rate of 20%~30%. Combined with its antioxidant and lipid-lowering properties, these findings provide crucial theoretical and experimental support for the development of Grifola frondosa applications in functional foods, health supplements, and cosmetic ingredients.