A water-soluble polysaccharide(VVP-1b) was obtained by isolating and purifying from the fruiting bodies crude polysaccharides of Volvariella volvacea through deproteinization,decoloration,DEAE-Sepharose Fast Flow ion-exchange column chromatography and Superdex-200 column chromatography.Its partial properties and structure were studied by HPLC,UV,IR spectrum.The results showed that VVP-1b was a homogeneous polysaccharide with typical absorption of polysaccharide.β-glucosidic bond was determined by IR.The total sugar content of VVP-1b was 88.7%,the protein content of VVP-1b was 7.8% and uronic acid content was 27.6%.Its Mw was 5.84 × 105 Da.VVP-1b consists of Ara,Man,Gal,Glc,in the molar ratios of 4.0∶ 1.0∶ 1.4∶ 35.4.VVP-1b was a homogeneous acidic polysaccharide with β-pyranose glycosidic bond.