The invention discloses a preparation method of a culture medium for cultivating hypsizigus marmoreus, belonging to the technical field of edible fungus cultivation. The method comprises the following steps: 1. taking bagasse, peanut shells and bamboo sawdust, pulverizing to obtain powder of which the particle diameter is 1-2mm, and soaking in a NaOH solution to obtain swollen residues; 2. uniformly mixing fungus residues, rape seed cakes, chicken manure, wheat straws, beech wood cuttings, fly ash, Eichhornia crassipes, water and a fermentation inoculum with the swollen residues, and carrying out fermentation to obtain a fermented fertilizer; 3. mixing the fermented fertilizer with urea, potassium phosphate, lime powder, ammonium lignosulfonate, zeolite powder, humic acid and peach gum powder, regulating the pH value, and controlling the water content at 65-67%; and 4. carrying out high-pressure steam sterilization, cooling, and packaging in a fungus bag, thereby obtaining the culture medium. The hypsizigus marmoreus culture medium disclosed by the invention has balanced nutrition, contains multiple minor elements, and is capable of shortening the hypsizigus marmoreus growth period and enhancing the yield and quality of the hypsizigus marmoreus.