Abstract: Using wild type Sanghuangporus vaninii from Changbai Mountain as the raw material, this study investigated the extraction process, antioxidant activity, and protective effect against cell damage on pancreatic β cells of polysaccharide extract from S. vaninii (YSP). The extraction process of YSP was optimized through single-factor experiments and response surface methodology. The monosaccharide composition and structural characteristics were analyzed using HPLC and FT-IR, respectively. The in vitro antioxidant activity of YSP was assessed, and its protective effect on H₂O₂-induced pancreatic β cells was examined. The findings revealed that the optimal extraction conditions for polysaccharides from S. vaninii were: cellulase enzyme amount of 1.5%, enzymolysis duration of 2.0 h, and enzymolysis temperature of 45 ℃. Under these conditions, the polysaccharide extraction rate reached 3.31%. YSP was predominantly composed of mannose, ribose, and rhamnose at a molar ratio of 16.45∶1.18∶1.00 featuring both α- and β-pyranose configurations. The results of antioxidant activity indicated that YSP could significantly scavenge DPPH, ABTS^+·, and O₂^-·. The protective activity of YSP on pancreatic β cells demonstrated that treatment with varying concentrations of YSP significantly inhibited H₂O₂-induced cell damage in INS-1 cells. It was observed that YSP increased cell viability, reduced ROS production and LDH levels, and enhanced the activitives of SOD, CAT, and GSH. These findings provide a basis for further research and development of polysaccharides from S. vaninii as functional foods.