Abstract: To optimize the extraction technology of polysaccharides from Agaricus blazei Murrill mycelium, and the antioxidant activities of polysaccharides, the single-factor experiment was carried out by using ultrasonic assisted extraction method with temperature, time, solid-liquid ratio and times. Based on the single-factor results, response surface methodology was used to determine the extraction technology conditions of polysaccharides from A. blazei Murrill. In vitro antioxidation activity of the A.blazei Murrill polysaccharides was evaluated by DPPH, ·OH and O₂^- free radicals scavenging method comparing with ascorbic acid.The results showed that the optimal extraction technology of polysaccharides from A. blazei Murrill were as follows:extraction temperature of 94 ℃, extracting time of 2.1 h, solid-liquid ratio of 1 ∶ 35 ( g ∶ m L) , and extraction times of 3, the model-predicted and experimentally measured values of polysaccharide yield were 9.41% and 9.30%, respectively, revealing a relative error of only 1.17% between them.Thus, the conditions were optimal for polysaccharide extraction.The polysaccharides from A.blazei Murrill had a capacity to scavenge DPPH free radical, hydroxyl free radical, superoxide anion, and the IC₅₀ was0.184, 0.316 mg/m L and 0.198 mg/m L, respectively.Antioxidant activity of A.blazei Murrill polysaccharides was weaker than those of vitamin C.