The selenium polysaccharide was prepared by chemical synthesis methods taking Jiyuan rubescens polysaccharides as raw materials. The structural characteristics of polysaccharides and selenium polysaccharides were analyzed by UV, FT-IR, SEM, TGA, and HPLC.The antioxidant capacity of rubescens polysaccharides and selenium polysaccharides were evaluated by four methods including DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) radical method and hydroxyl radical method. Results:The mass fraction of selenium in selenium polysaccharide was 1.35 mg/g. After the selenization modification, the basic skeleton of rubescens polysaccharides was retained, and the types of monosaccharides remain unchanged, but its stability and decomposition temperature were decreased, and the morphology of polysaccharides also changes significantly. The spherical and strip morphology increased, and the flake morphology decreased.In addition, in the in vitro antioxidation experiment,when the mass concentration of selenium polysaccharide was 1.6mg/mL, the scavenging rates of DPPH radicals, ABTS radicals, and OH radicals were 68.68%, 86.69%, and 45.12%, respectively, which were all stronger than Rubescens polysaccharides.