The invention relates to a preparation method of edible fungus residue charcoal. The preparation method of the edible fungus residue charcoal is characterized by particularly comprising the steps of drying, crushing and sieving the edible fungus residues, mixing the sieved edible fungus residues with a zinc chloride solution uniformly, allowing the formed mixture to stand for 30 to 40 minutes, centrifugally separating the fungus residues, adding the fungus residues in a catalyst aqueous solution, performing magnetic stirring, performing hydrothermal carbonization, and performing centrifuging,washing and drying, wherein the catalyst aqueous solution is formed by mixing sulfuric acid with the mass concentration of 80 to 95 percent, phosphoric acid with the mass concentration of 60 to 85 percent and water according to the volume ratio of (1-2):(5-8):(20-40). According to the edible fungus residue charcoal prepared by a hydrothermal method, the specific surface area is large, the BET specific surface area reaches 962m<2>/g, the porosity is high, the pore diameter distribution is uniform, the stability is high and the yield is high; and the edible fungus residue charcoal has excellentadsorption property on heavy metal ions, and the removal rate on the heavy metal ions can reach 82.4 percent of that of the edible fungus residue charcoal in initial use after the edible fungus residue charcoal is reused for 20 times.