Objective: Develop the industrial production of Lentinus edodes stalk polysaccharides. Methods: Using the yield of polysaccharides as an indicator, uniform design experiments were used to optimize the extraction process parameters. Four methods were used to determine the antioxidant activity of polysaccharides and compared with the traditional hot water extraction method. Results: The optimal process conditions for the flash-assisted extraction of Lentinus edodes stalk polysaccharides were as follows: flash extraction time 120 s, ratio of liquid to material 40∶1 （mL/g）, hot water extraction time 105min, temperature 50 ℃, extraction twice. Under these conditions, the yield of polysaccharides was （5.03±0.22）%, which was basically consistent with the predicted value of the model and 1.82 times higher than that of traditional hot water extraction method. Lentinus edodes stalk polysaccharides had strong Fe³⁺ reduction ability, total antioxidant capacity, ·OH and DPPH· scavenging capacity, and showed a dose-effect relationship. The antioxidant activity of polysaccharides obtained by flash-assisted hot water extraction was stronger than that of the traditional hot water extraction, but weaker than that of vitamin C. Conclusion: Flash-assisted hot water extraction is beneficial to the extraction of polysaccharides from Lentinus edodes stalks, and can maintain its antioxidant activity.