The invention discloses a preparation method for selenium-enriched Coprinus comatus mycelia, which is characterized in that the preparation method comprises the following steps of: 1) taking Coprinus comatus spawns and culturing the Coprinus comatus spawns in a slant culture medium to obtain Coprinus comatus slant spawns; 2) taking and inoculating the Coprinus comatus slant spawns obtained at thestep (1) into a shake flask culture medium for shaking bed culture to obtain liquid spawns; and 3) taking and inoculating the liquid spawns obtained at the step (2) into a selenium-containing fermentation culture medium for fermentation, stopping fermentation till the fermentation liquid is transparent, the flavor is fragrant, the mycelium biomass is 20-30g/L and the pH is 5-7, and obtaining the selenium-enriched Coprinus comatus mycelia. The invention additionally discloses a preparation method for selenium-enriched Coprinus comatus powder. Since Coprinus comatus is used as carriers to realize the organic transformation of selenium, the biological functions of the Coprinus comatus and the selenium are compensated.