The effects of different concentration of NAA on biomass and mycelia polysaccharide content and the antioxidant activity of mycelia polysaccharide of Morchella angusticeps Peck were studied in fermentation medium. The results showed that appropriate concentration of NAA could increase the biomass and mycelia polysaccharide content.The treatment of fermentation medium with 2. 0μg / mL of NAA could significantly increase the hyphae dry weight and mycelia polysaccharide content per gram,wherein the maximum respectively was 9. 873g / L and 429. 5mg,respectively increased 34. 89% and 15. 68% comparing to no NAA. Appropriate concentration of NAA could also improve the scavenging action of mycelia polysaccharide to DPPH,while it decreased the scavenging action of mycelia polysaccharide to hydroxyl radical.