Abstract: In this paper, selenium polysaccharide (sKGP) extract was obtained by extraction, separation and purification of selenium-enriched creeson grape, then its physicalchemical properties, structural characteristics and antioxidant activity were studied. The selenium polysaccharide was extracted by ultrasonic-assisted enzymatic, separated and purified by diethylaminoethyl cross-linked dextran gel chromatography column. Its active functional groups and structures were identified by UV, LC-MS, fourier IR and SEM, and the antioxidant activity indexes were also analyzed. The results showed that the content of selenium in sKGP-3 was (0.642±0.038) mg/kg, and the purified sKGP-3 contained almost no nucleic acid and protein, the sKGP-3 was composed of rhamnose, xylose, arabinose, mannose, glucose and fructose, the molar ratio was 0.172:0.743:0.718:0.082:4.540:0.093. The sKGP-3 had the structure of Se=O, Se-H and typical characteristic peaks of polysaccharides, and the shape of the sKGP-3 was mainly lamellar and filamentous, belonging to amorphous state. The evaluation of antioxidant activity in vitro showed that the sKGP had higher antioxidant activity than the polysaccharide (KGP) of the same concentration before purification, the total antioxidant capacity of sKGP was 8.499 μmol/mL, and the scavenging capacity of DPPH, hydroxyl radicals and ABTS⁺ radicals were 69.7%, 85.8% and 92.5%, respectively.