The invention relates to a method for extracting polysaccharide from fresh hedgehog hydnum, which comprises the following steps of: leaching the fresh hedgehog hydnum in water at the temperature of between 55 and 65 DEG C for 2 hours, and filtering to obtain filter liquor; regulating a pH value of the filter liquor to between 4.0 and 4.5; performing chromatography on a HD-3 resin column for decoloring and deproteinizing, and performing ultrafiltration grading by using ceramic ultrafiltration membranes of which the molecular weight cutoff is 50 KD and 10 KD; and concentrating intermediate trapped fluid and spray-drying to prepare the polysaccharide, wherein the total recovery is 0.96 percent, and the purity is between 71 and 83 percent. The method has the advantages of high purity of the obtained hedgehog hydnum polysaccharide, simple and feasible process, no need of a drying process or an organic solvent, recycled resin, energy conservation, pollution reduction, and particular suitability for continuous industrial production.