Abstract: The hot-water extraction of polysaccharides from the mycelia of Agaricus blazeia grown on a selenium-enriched medium was optimized to facilitate product development of health foods with the functional ingredient. A single factor followed by an orthogonal experiment was carried out to show the extraction yield to be significantly affected by the altered processing conditions. The optimized extraction conditions included a sample/water ratio of 1/35 (g·mL^-1), an ethanol concentration for precipitation at 90%, a temperature of 85℃, and 3 repeated cycles that lasted 3.5 h. As a result, a yield on polysaccharides reached 69.5 mg·g^-1; and the content of selenium in polysaccharides reached 12.1 μg·g^-1(dry weight of mycelium). The procedures were simple, stable, practical, and appropriate for the extraction.