NOVELTY - Preparation device comprises first grade breaking roller sieve, secondary breaking roller sieve, first level magnetic separation device, biological preprocessing chamber, subdivision selection unit, one stage roller sieve, secondary level magnetic sorting device, four cylinder sieves, aerobic fermenting cabin, crusher, and briquetting machine. The first and secondary level magnetic separation devices are respectively provided with top part garbage feeding opening and waste outlet.    USE - Preparation device used for preparing household garbage derived fuel.    ADVANTAGE - The device produces treated garbage that is dry and harmless without addition of solid chloride agent and binder, treated garbage thus reducing dioxin. It releases heavy metal, provides good energy recovery, stable refuse derived fuel (RDF) property and extrusion property, and provides garbage derived fuel having high heat value.    DETAILED DESCRIPTION - Preparation device comprises first grade breaking roller sieve, secondary breaking roller sieve, first level magnetic separation device, biological preprocessing chamber, subdivision selection unit, one stage roller sieve, secondary level magnetic sorting device, four cylinder sieves, aerobic fermenting cabin, crusher, and briquetting machine. The first and secondary level magnetic separation devices are respectively provided with top part garbage feeding opening and waste outlet. The garbage feeding opening is provided with feeding belt having lower part provided with metal discharge hole for metal material. The waste material belt is connected with material discharging opening and material output belt. The separation device is further provided with electromagnetic separator having lower part set with reversing bounce belt, feeding belt and magnetic separation belt. The reversing bounce belt is running in parallel direction with feeding belt to provide rebound effect. The two stage magnetic separating device is connected to first level magnetic separation roller sieve, which is connected with secondary magnetic separation roller sieve and bounce sorting machine. An INDEPENDENT CLAIM is included for preparation of household garbage derived fuel by breaking and sieving solid waste; sieving garbage; sending remaining garbage into primary magnetic separation device to separate ferromagnetic material, inert material and organic material; sending organic material through belt conveying device to biological pre-processing chamber for biological pre-treatment; preprocessing household garbage via facultative bio-fermentation without ventilation at 35-65 degrees C to reduce wastewater content at 30-60%; performing mechanical sorting to sort out metal with different grain diameters; introducing remaining material into aerobic fermentation storehouse for aerobic composting; aerobic composting domestic garbage twice at 40-70 degrees C under negative ventilation; sorting garbage; crushing product after aerobic composting; and extruding to obtain household garbage derived fuel.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of preparation device for preparing household garbage derived fuel.