Abstract:To optimize the extraction technology of polysaccharide from Ganoderma lucidum by ultrasonicassisted crushing method，compare the antioxidant activity of G.lucidum and the optimal antioxidant parts in vitro were selected.On the basis of single factor experiment，the effect that material-liquid ratio，ultrasonic time，ultrasonic power work on yeild of G.lucidum polysaccharide was investigated. Box-Behnken central composite design with response surface experiment was used to optimize conditions. Its antioxidant capacities were investigated according with scavenging of DPPH·radicals and hydroxyl radicals and reducing power that was GLP40，GLP60，GLP80 from G.lucidum polysaccharide by the method of ethanol fractional precipitation.The results of optimum extraction conditions by response surface experiment that material-liquid ratio was 25 ∶1（mL/g），ultrasonic time was 60 min，ultrasonic power was 760 W，G.lucidum polysaccharides yield was 3.60%.The ratio of GLP40，GLP60 and GLP80 was 45 ∶29 ∶26 and it had certain antioxidant activity.GLP80 had the strongest scavenging ability of DPPH free radicals，GLP40 had the strongest scavenging ability of hydroxyl radicals，and GLP60 had the best reducing power.