Abstract: Using alkaline digestion and fractionations by precipitation with potassium salt and quaternary ammonium salt, two fucose-containing acidic polysaccharides, HL-S and HL-P were obtained from the dried body wall of Holothuria leucospilota(Brandt). Both polysaccharides were shown to be pure substances by electrophoretic and gel chromatography as well as ultracentrifugal analysis.According to analytical and physical data, HL-S seemed to be polyfucose sulfate, which was found in most sea cucumbers investigated, and HL-P was identified as a sulfated mucopolysaccharide consisted of galactosamine, glucouronic acid, fucose and sulfate with the molar ratio of 1:0.94:0.84:3.60 repectively. The specific rotation, intrinsic viscosity, sedimentation constant and molecular weight of these two polysaccharide were all presented.Studies on biological activity showed that HL-P is a powerful inhibitor of thrombin in vitro and also showed significant inhibitory effects on tumor growth in mice.