NOVELTY - A Coprinus culture base material composition and its preparation method are claimed. The composition comprises 40-4200 pts. wt. dried bean residue, 60-1800 pts. wt. corn core, 2-180 pts. wt. lime powder, 3-300 pts. wt. lime, 1- 90 pts. wt. gypsum powder, 1-90 pts. wt. light calcium carbonate, and 0.5-60 pts. wt. fertilizer composition. The composition is prepared by diluting the bean residue using diluted hydrochloric acid solution, adjusting pH value, composting mixture, adding corn core and lime powder, and fermenting the mixture.    USE - As Coprinus culture base material (claimed).    ADVANTAGE - The culture base material is environmentally-friendly, and improves biomass of the Coprinus.    DETAILED DESCRIPTION - A Coprinus culture base material composition and its preparation method are claimed. The composition comprises 40-4200 pts. wt. dried bean residue, 60-1800 pts. wt. corn core, 2-180 pts. wt. lime powder, 3-300 pts. wt. lime, 1- 90 pts. wt. gypsum powder, 1-90 pts. wt. light calcium carbonate, and 0.5-60 pts. wt. fertilizer composition. The composition is prepared by diluting the bean residue using diluted hydrochloric acid solution, adjusting pH value of the mixture to less than 3, composting the mixture, adding corn core and lime powder to the compost, adding lime, gypsum powder, light calcium carbonate and fertilizer composition, uniformly blending the mixture, adjusting pH value of the base material to more than 11, fermenting the mixture, and adjusting pH value of the fermented mixture. An INDEPENDENT CLAIM is included for method for preparing the above-mentioned culture base material, which involves (a) cleaning the fresh bean residue, drying the bean residue until the bean residue has water content not greater than 40%, adding 0.5-5 wt.% diluted hydrochloric acid solution, adjusting pH value of the solution to not greater than 3, composting the mixture at 45-55 degrees C for 6-20 days and turning the compost for 1-4 days, (b) crushing the corn core, adding lime powder to the crushed core, composting the mixture at 45-65 degrees C for 6-20 days and fermenting the mixture, and (c) mixing the mixtures obtained in step (a) and step (b), adding gypsum powder, precipitated calcium carbonate and fertilizer, adjusting the pH of the mixture using not greater than 11 at 50-60 degrees C, fermenting the mixture for 7-30 days and adjusting pH of the fermented mixture.