Abstract: Rice was used as materials for Cordyceps taii fermentation, the content of Cordyceps taii polysaccharide was increased through optimizing fermentation conditions. Single-factor and multi-factor experiments were used to optimize the solid fermentation conditions of Cordyceps taii producing polysaccharide. The results of Plackett-Burman test showed that fermentation temperature, inoculation quantity and the ratio of material to water were main affecting factors for the content of Cordyceps taii polysaccharide. Then the steepest ascent experiment and Box-Behnken experiment were conducted to obtain the optimum conditions of Cordyceps taii producing polysaccharide as follows: Fermentation temperature 25 ℃, inoculation amount 8%, the ratio of material to water (g/mL) 1:1.5, the weight of substrate 10 g and the fermentation time 5 days. The content of Cordyceps taii polysaccharide was 5.31%±0.11%, and the error was 0.93%±1.8% comparing with the theoretical value. It would provide a theoretical basis for the industrial production of Cordyceps taii polysaccharide and a theoretical reference for other Cordyceps spp. producing polysaccharide by solid fermentation.