Abstract: In order to investigate effects of exogenous additives on mycelium yield and intracellular and extracellular polysaccharide content in liquid fermentation medium of Phellinus igniarius, oleic acid, α-naphthalene acetic acid, vitamin B₂ and water extract of mulberry white bark were added in different concentrations, and mycelium yield and intracellular and extracellular polysaccharide content were measured after liquid fermentation．Experimental results showed that, four kinds of exogenous additives could significantly increase mycelium yield and polysaccharide content of Phellinus igniarius（P<0.05）, among which oleic acid was the best exogenous additive．When oleic acid concentration was 2.4 mL/L, mycelium yield was the highest, reaching 2.86 mg/mL, which was 7.15 times that of blank control．Under this oleic acid concentration, extracellular polysaccharide content was the highest, reaching 56.04 mg/mL, which was 7.71 times that of blank control．When oleic acid concentration was 1.2 mL/L, polysaccharide content in the cell of Phellinus igniarius, was the highest, reaching 60.07 mg/g, which was 3.96 times that of blank control．The other three additives could also increase mycelium and extracellular and extracellular polysaccharide production（P<0.05）．Four kinds of exogenous additives in the experiment were inducible factors to effectively increase mycelium and polysaccharide yield of liquid fermentation of Phellinus igniarius．