NOVELTY - Preparing biomass fuel based on sludge-straw-biomass fuel raw coal involves adding raw limestone to dewatered sludge after using aluminum salt coagulant application, where the mass percent of limestone sludge is 3%, the pre-treated sludge of aluminum oxide based on Al2O3 is not less than 5 mass%, and water content is less than 70%, the straw cutting and crushing to particle size of less than 2, preparing combustion heat value is not less than 25000 focus/kg of raw coal; performing aerobic composting the raw coal and sludge-straw mixture to mix; pressing the sludge-straw-coal mixture, and forming biomass fuel.    USE - For preparing biomass fuel based on sludge-straw-biomass fuel raw coal; and as artificial wetland.    ADVANTAGE - The method quickly dehydrates the raw material; is capable of passivating heavy metal; reduces raw coal combustion releasing system; provides slag high Ca, Al and Fe content of absorption performance; and is used as phosphorus removing agent in the sewage treatment process.    DETAILED DESCRIPTION - Preparing biomass fuel based on sludge-straw-biomass fuel raw coal involves adding raw limestone to the dewatered sludge after the aluminum salt coagulant used as pre-processing, where the mass percent of limestone sludge is 3%, the pre-treated sludge of aluminum oxide based on Al2O3 is not less than 5 mass%, and water content is less than 70%, the straw cutting and crushing to particle size of less than 2, the straw water content is less than 60%, preparing combustion heat value is not less than 25000 focus/kg of raw coal; dehydrating: aerobic composting sludge is sludge, straw, the raw coal mass ratio of 3:3:3, weighing first step, straw and raw coal, and the mud and straw, carrying out aerobic compost ventilation for 15-50 days, every 5 days for the first time, the sludge-straw mixture to water content is less than 50%; mixing the sludge-straw mixture with the raw coal to obtain sludge-straw-coal mixture, press forming: pressing the sludge-straw-coal mixture, and forming biomass fuel, the forming pressure is not less than 300t, the biomass fuel size is as follows: the height is less than 15 cm, and diameter is less than 18 cm.