Abstract: In order to explore the in vitro antioxidant and immune activities of the intracellular and extracellular C. sinensis polysaccharides and their dose-effect relationship, polysaccharides were extracted from C. mycelium and fermentation broth by water extraction and alcohol precipitation method, sevege method and activated carbon adsorption method, respectively. The antioxidant and immune activities of intracellular and extracellular polysaccharides were analyzed in vitro. The results showed that the optimal extraction conditions were liquid/solid ratio 95:1 mL/g, extraction temperature 65℃ and extraction time 1.5 h. The results of UV and IR spectra of C. sinensis polysaccharides showed that the polysaccharide samples contained nucleic acids and proteins in different degrees, and were acidic heteropolysaccharides with β-glycoside bonds and pyranose rings. This study also confirmed that the polysaccharides from the self-fermentation liquid and the fermented cordyceps powder had a good free radical scavenging ability and showed a certain dose-effect relationship. The effects of polysaccharides on immune cells were further compared, and it was found that both polysaccharides could promote the proliferation of RAW 264.7 macrophages and promote the release of NO, and the activity of polysaccharides in fermentation broth was higher than that of intracellular polysaccharides, and there was a significant difference with LPS group (P< 0.001). Therefore, the fermented liquor collected from C. sinensis polysaccharides extract showed good antioxidant activity and immune activity in vitro, which is expected to develop as new drugs to improve immunity or new functional food resources, such as natural antioxidant.