Abstract: To optimize the extraction technology of polysaccharides from Lactarius deliciosus,and the antioxidant activities of the polysaccharides. The single-factor experiment was carried out by using ultrasonic-assisted extraction method with temperature,time,solid-liquid ratio and times. On the basis of single-factor experiments,a four-factor,three-level Box-Behnken central composite design was utilized for mathematical modeling for polysaccharide yield,followed by responses surface analysis of the relationship between the function and the four variables. In vitro antioxidation activity of the L. deliciosus 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 L. deliciosus were as follows:extraction temperature of 92.8 ℃,extracting time of 1.6 h,solid-liquid ratio of 1:28 (g:mL),and extraction times of 3.Under these conditions,the model-predicted and experimentally measured values of L. deliciosus polysaccharide yield were 10.60% and 10.41%,respectively,revealing a relative error of only 1.79% between them. Thus,the conditions were optimal for polysaccharide extraction. The polysaccharides from L. deliciosus had a capacity to scavenge DPPH free radical,hydroxyl free radical,superoxide anion,and the IC₅₀was 0.855,1.147 and 1.126 mg/mL,respectively. Antioxidant activity of L. deliciosus polysaccharides was weaker than those of vitamin C. The extraction technology was efficient,simple low cost and applicable for the extraction of polysaccharides form L. deliciosus and L. deliciosus polysaccharides has significant in vitro antioxidation.