The invention relates to a culturing base material and preparing method for growing agaricus bisporus which uses marsh dregs from straw raw material to produce marsh gas. The raw material component for culturing base material comprises marsh dregs, dairy manure, bean cake powder, lime powder, plaster powder, light calcium carbonate, ordinary superphosphate and carbamide. The marsh dregs of straw raw material is taken out, drained, processed in aerobic condition and dried to a condition of water ratio lower than 65 percent or the marsh dregs are sunned and dried to condition water ratio of lower than 15 percent for storage and backup. The invention achieves reuse of marsh dregs to a maximum extent, therefore, growing raw material source is widened to achieve the agaricus bisporus growing raw material source with reliability, universality and growing high yielding. The normal growing cost is decreased by around 50 percent and output is raised by 10 percent. The invention is beneficial to develop circular economy and in accordance with the demand for searching and using new raw material resources of edible fungi industrialization development at the present stage.