Abstract: The optimum processing conditions of enzyme-assisted extraction of polysaccharides from Hypsizigus marmoreus were studied by Box-Behnken statistical design. The antioxidant activities of polysaccharides from Hypsizigus marmoreus were investigated by 1 , 1 - diphenyl - 2 - picrylhydrazyl ( DPPH ) radical scavenging activities, hydroxyl radical scavenging activities and reducing power. The results showed that when the extraction parameters were controlled at complex enzyme (i.e. papain and cellulase mixed at a mass ratio of 1∶1) amount 0.9% , enzymolysis pH5.4, enzymolysis temperature 55.6℃ , and extraction time 2.8h, the polysaccharides yield could be up to 4.68% . The positive liner correlations between the antioxidant activity and concentration of polysaccharides were found over the investigated ranges. IC 50 values against DPPH and hydroxyl radicals were 78.5μg/mL and 170.5μg/mL, respectively.