Objective: To explore the structure， immunomodulatory activity and antioxidant activity in vitro of ploysaccharides from Radix asparagi. This study will provide a basis for subsequent research on Radix asparagi polysaccharides. Methods: The polysaccharide of Radix asparagi was extracted and purified by the methods of water extraction and alcohol precipitation and Sevage. The scavenging ability of DPPH free radical， superoxide anion and hydroxyl free radical were determined. Results: The content of crude polysaccharide was 63.13% and that of freeze-dried powder was 73.98%. When the concentration of ethanol reached 80%， the polysaccharide with small molecular weight could be separated. This product contained rhamnose， arabinose， galactose， glucose， xylose， mannose， galacturonic acid. It had no obvious effect on the proliferation and immunity of spleen lymph. The antioxidant capacity was weak. Conclusion: The method used in this study was simple and accurate， which could provide reference for the extraction， purification and in vitro antioxidant activity of polysaccharides from Radix asparagus and other similar medicinal materials. To understand the monosaccharide composition of Radix asparagus polysaccharide. However， the antioxidant capacity of 80% alcohol precipitated polysaccharide is not obvious， which needs further study.