The polysaccharides contents and antioxidant activity of Sanicula astrantiifolia Wolff were detected. The results showed that: the polysaccharides contents in aboveground and underground part of Sanicula astrantiifolia Wolff were 2.155 and 2. 329 g/100 g respectively; when the polysaccharides concentrations were more than 100.8 µg/mL, the reducing ability of polysaccharides was higher than rutin; the inhibition ability to the superoxide anion free radical ( O2ˉ· ) gradually increased with the increasing of mass concentration; when the polysaccharides concentrations were more than 13.44 µg/mL, the inhibition rate was higher than rutin; The scavenging capacity of DPPH radical was higher than rutin when the polysaccharides concentrations were more than 42.00 µg/mL; the scavenging ability to hydroxyl radical (·OH) was significantly higher than rutin, and when the mass concentration was 8.06 µg/mL, the ability reached 95.40%; the polysaccharides of Sanicula astrantiifolia Wolff have good antioxidant activity.