NOVELTY - Preparing compost, comprises mixing straw, rice husk, urea, mushroom, calcium superphosphate, gypsum, and lime to obtain culture material, stacking the culture material, placing the culture material into a mushroom planting chamber, fermenting, adding strain, then mixing with the material for seedling, covering the material, when hypha grow on the material layer, using fine mud and rice husk ash, mixing soil with formaldehyde, then spraying, sterilizing, disinfecting the bed by spraying diluted deltamethrin to control insect and pests, and maintaining good indoor ventilation.    USE - The method is useful for preparing compost for cultivating mushroom (claimed).    ADVANTAGE - The method is capable of preparing compost without pollution and with increased mushroom yield of 18%.    DETAILED DESCRIPTION - Preparing compost, comprises weighing 75-80 wt.% of straw, 5.5-6 wt.% of rice husk, 1.5 wt.% of urea, 1-6 wt.% of mushroom, 1.8-2 wt.% of calcium superphosphate, 3.8-4.1 wt.% of gypsum, 3.8-4.1 wt.% of lime, and 2.8-3 wt.% of lime, and uniformly stirring and mixing to obtain culture material, outdoor stacking the culture material for 12-18 days, placing the culture material into a mushroom planting chamber, primary fermenting by heating the chamber at 65 degrees C for 6-8 hours, then reducing the temperature to 50 degrees C and maintaining for 5 days, adding 2/3 of strain into an inner side of the chamber at first time, then mixing the strain with the material, adding balance amount of 1/3 of strain on a surface layer of the material for seedling, then adding into 2 bottles, holding at 50 degrees C to room temperature until relative humidity is 60-70%, covering the material to a thickness of 3-4 cm with a water density of 2.5 kg, when hypha grow on the material layer, using fine mud and rice husk ash at weight ratio of 1:20, mixing soil with formaldehyde, then spraying on the covered material, sterilizing, adjusting pH value of the material using weak alkaline, covering the material with soil for 15 days until hypha is twisted into primordia form, keeping surface of the bed to wet, maintaining the indoor temperature to 40-45 degrees C and relative humidity to 85-90%, disinfecting the bed by spraying diluted deltamethrin to control insect and pests, and maintaining good indoor ventilation.