Abstract: The hydrolysis of seafood mushrooms by cellulase for the extraction of ploysaccharides was optimized using response surface methodology. The antioxidant activity of polysaccharides from seafood mushrooms in vitro was evaluated by DPPH and OH free radical scavenging ability with V_C as reference. The results showed that the optimal extraction parameters were: cellulase content was 0.56%, enzymatic hydrolysis time was 112 min, liquid-material ratio was 20∶1, and the average yield was 1.50%. The results of in vitro antioxidant experiment indicated that when the mass concentration of polysaccharides was 5 mg/mL, the scavenging rate of DPPH and ·OH radical was 88.51% and 80.64% respectively, but both were lower than that of V_C. The results showed that the optimized extraction process was stable, reliable and feasible.