Abstract: 【Objective】 In order to improve the production of extracellular polysaccharides of Agrocybe aegerita, the suitable medium and related culture conditions for liquid fermentation were optimized. 【Method】 Based on the yield of extracellular polysaccharides, some fermentation conditions such as carbon source, nitrogen source and concentration, initial pH, shaking speed and culture time were explored by single factor test. The optimized conditions of submerged fermentation increased the yield of extracellular polysaccharide produced by the mycelium of A. aegerita, and the yield of extracellular polysaccharide was measured by the phenol-sulfuric acid method. 【Result】 The optimum conditions for the production of extracellular polysaccharides by liquid fermentation of A. aegerita were as follows: soluble starch was used as carbon source and the concentration was controlled at 20-40 g/L; L-glutamine was used as nitrogen source and the concentration was controlled at 2 g/L; the initial pH was controlled at 7.0, the shaking speed was controlled at 180 r/min, and extracellular polysaccharides were cultured at 26℃ for 12 d. 【Conclusion】Under the above-mentioned fermentation conditions, the yield of extracellular polysaccharide was 1.08 g/L, in which the content of polysaccharide was 71.73% and the content of protein was 8.62%. This provided an theoretical basis for the industrial production and application of A. aegerita polysaccharides.