The　structural　characteristics,　thermal　stability,　rheological　properties,　and　antioxidant　activity　of　oyster　polysaccharide　(OPS)　were　studied.　The　oyster　polysaccharide　was　extracted　by　enzymatic　hydrolysis　and　Sevage　method.　The　phenol-sulfuric　acid　method,　Coomassie　brilliant　blue　binding　method,　high　performance　liquid　gel　permeation　chromatography　(HAGPC),　PMP　derivatized　polysaccharide　hydrolysate　method,　scanning　electron　microscope,　and　UV-visible　and　infrared　spectroscopy　analysis　of　total　sugar　content,　molecular　weight,　monosaccharide　composition,　group　composition,　microstructure,　rheology　properties,　and　antioxidant　activity.　Results　showed　that　OPS　was　a　heteropolysaccharide　with　a　molecular　weight　of　623.　24　kDa.　It　was　composed　of　glucose,　mannose,　ribose,　galactose,　xylose,　arabinose,　and　fucose,　the　main　glucose　with　a　content　of　95.　35%,　which　was　produced　by　β-polysaccharide　formed　by　linking　glucose　by　glycosidic　bonds.　The　microscopic　surface　of　OPS　was　relatively　loose　and　had　a　coral-like　structure.　OPS　existed　in　characteristic　groups　of　carbohydrates,　with　pyran　rings　and　triple　helical　structures.　The　thermogravimetric　analysis　showed　that　OPS　had　good　thermal　stability.　The　polysaccharide　solution　was　a　shear-thinning　pseudoplastic　fluid,　and　the　0.　5%　(mass　fraction)　OPS　solution　had　good　viscosity.　The　median　inhibitory　concentrations　(IC50　values)　of　OPS　on　DPPH　radical,　ABTS　cationic　radical,　ferrous　ion　chelating　ability,　and　hydroxyl　radical　were　0.　36,　2.　71,　4.　15,　and　1.　21　mg　/　mL,　respectively.　Results　provided　a　basis　for　further　developing　the　application　value　of　oyster　polysaccharides,　especially　in　thickening　agents　and　antioxidants　and　provided　a　reference　for　the　comprehensive　development　and　utilization　of　oyster　resources　and　the　promotion　of　high-value　and　efficient　processing　of　oysters.　©　2022　China　National　Research　Institute　of　Food　and　Fermentation　Industries　Co.　Ltd.　All　rights　reserved.