Abstract: Objective:The polysaccharide fractions and antioxidant activities of Agaricus bisporus protein powder waste were analyzed. Method:The Agaricus bisporus fruitbody protein extracted after residue was used as material. Agaricus bisporus crude polysaccharide was prepared using ultrasonic hot water extractive method,Sevage method,D101 macroporous resin and alcohol precipitation. The purified polysaccharide was obtained by DEAE-52 chromatography column. By scanning electron microscopy(SEM),infrared spectroscopy(IR)method for identification of physical and chemical properties of the purified polysaccharide. The antioxidant activity of the purified polysaccharide was evaluated by scavenging DPPH free radical,superoxide anion free radical and ABTS free radical,and protecting the yeast cells treated with H₂O₂.The activities of T-SOD,MDA and GSH-Px in the supernatants of H₂O₂oxidative damage were detected. Results:Three fractions(ABPS-I,ABPS-II and ABPS-III)were isolated and purified from the crude polysaccharide of Agaricus bisporus. Studies showed that ABPS-III had the strongest scavenging capacity for DPPH radicals. The content of polysaccharide from ABPS-III was 89.12%,and SEM had hexahedron structure,and IR analysis showed that it had obvious characteristics of carbohydrate compounds. The EC₅₀ value of scavenging DPPH,superoxide anion and ABTS radical of ABPS-III was 1.48,1.85,1.30 mg/mL,respectively. Oxidative damage to yeast cell protection experiments showed that ABPS-III could significantly improve the survival rate of injury of yeast cell oxidation,at the concentration of 25 mg/mL,the protection rate of 42.58%. Enzyme activity assay showed that after adding ABPS-III,compared with the oxidized injury group,the activity of T-SOD and GSH-Px in the supernatant of yeast cells increased by 337% and 102% respectively(p<0.01),and the content of MDA decreased by 35.17%(p<0.05). Conclusion:Agaricus bisporus polysaccharide ABPS-III has strong antioxidant activity.