The fermentation conditions of Coprinus comatus on the yield of extracellular polysaccharide were studied. The result showed that the optimum medium composition was as follows:3.0% maize powder, 1.0% yeast extract, 2.0% glucose,KH_2PO_4 0.20%, MgSO_47H_2O 0.15%,VB_1 15 mgL~(-1) and the optimum shaking culture conditions were 100 mL medium in size 250 mL,temperature 22,pH6.1,inoculation 10% for 4 days.