Abstract: A fungus numbered F4539 was isolated from wild Cordyceps sinensis and identified by morphology and molecular biological identification, in addition, the antioxidant activity for the fermentation products were studied. The results demonstrated that F4539（GenbankKU359775） had relatively high similarity in evolution with Hirsutella sinensis（AJ309355）, it was confirmed that F4539 was Hirsutella sinensis; Antioxidant activity tests showed that the DPPH antioxidant activity was 75.39% with a concentration of 20 g/L ethanol extract from F4539 fermentation products, which was higher than the same concentration of ethanol extracts from the certain commercial Cordyceps sinensis mycelium capsule. Further research showed that the IC₅₀ of F4539 fermentation products and commercial Cordyceps sinensis mycelium capsule were 5.96 g/L and 11.61 g/L respectively. It was shown that the antioxidant activity was higher in F4539 fermentation products than the commercial Cordyceps sinensis mycelium capsule.

Key words: Cordyceps sinensis, Hirsutella sinensis, antioxidant