Abstract: ″Ping 109″, a strain of oyster mushroom with high-yield, is bred by Shaanxi Provincial Institute of Microbiology which is suitable for cultivation in Guanzhong regions. Based on the strong ability of oyster mushroom in selenium enriching, cultivation experiment was conducted by adding certain concentration of sodium selenite to the culture medium of ″ Ping 109″. The results showed that the highest enrichment of selenium was obtained when 40 mg/kg of sodium selenite was added in the culture medium consisting of 85% of cotton seed hull, 12% of wheat bran, 1% of sucrose, 1% of calcium superphosphate, 1% of gypsum powder,and the culture temperature during mycelium stage was 28 ℃. Meanwhile, under this culture condition, the biomass of ″Ping 109″was also improved. The results suggest that adding inorganic selenium to culture medium is not only able to improve the production of oyster mushroom, but also accelerates the enrichment of selenium within mushroom. Supplementation of inorganic selenium is recommended in cultivation of selenium-enriched oyster mushroom.