Abstract: To explore the extraction process and antioxidant activity of polysaccharide from Sophora tonkinensis Gagnep,the Sophora tonkinensis Gagnep was used for extracting polysaccharide with hot water. The effects of extraction temperature,extraction time and ratio of liquid to material on the extraction rate of polysaccharide were investigated. On the basis of single factor tests,the extraction technology of polysaccharide from Sophora tonkinensis Gagnep was optimized by response surface methodology(RSM). The extracted crude polysaccharide was precipitated and fractionated by ethanol,and the antioxidant activity of each alcohol component was evaluated by the methods of scavenging DPPH,ABTS⁺ radical and reducing ability,respectively. Results showed that,the optimum extraction conditions were as follows:The extraction temperature was 83 ℃,the extraction time was 133 min,the ratio of liquid to material was 30:1 mL/g. Under the optimal extraction conditions,the yield of polysaccharides from Sophora tonkinensis Gagnep was 3.98%. The crude polysaccharide obtained four components SGP50,SGP70,SGP80 and SGP90 by fractional alcohol precipitation. And the SGP90 showed the strongest antioxidant activity,especially in the DPPH free radical scavenging,which was significantly higher than other components(P<0.05).