Abstract:The study aims to explore the antioxidant activity of polysaccharide fraction from Sargassum horneri in vitro.Polysaccharide fractions with biological activity from Sargassum horneri were separated by Deae-Sepharose-Fast-Flow，and the components polysaccharide were scanned by infrared spectral.then The purified polysaccharides were evaluated on their antioxidant activities.In the end，four polysaccharides were obtained by gradient elution of sodium chloride.The four components of polysaccharides from Sargassum horneri showed characteristic absorption peaks by infrared spectroscopy，all of which compounds showed sugar characteristic absorption peaks in infrared spectrum.In the experiment of testing anti-oxidation activity.SF2 had the best antioxidation activity with DPPH·IC50was 0.499 μg respectively，strong reducibility and its ability to the scavenging O2-effect.Therefore，Sargassum horneri polysaccharides are expected to be new antioxidants.