NOVELTY - The method comprises pre-processing water-containing sludge, processing the sludge to be divided into inorganic hydrous sludge and organic matter containing sludge, selecting the hydrous organic matter containing sludge for removing iron in a post-treatment process, removing the organic matter as impurity in the sludge water, pretreating biomass raw material, crushing raw material to a length of less than 3 cm, mixing organic matter water-containing sludge and the raw material in a mass ratio of 7:3, stacking the mixture in a fermentation condition, and decomposing organic matter.    USE - The method is useful for producing fuel (claimed).    ADVANTAGE - The method is capable of producing the fuel in an economical and environmentally friendly manner.    DETAILED DESCRIPTION - The method comprises pre-processing water-containing sludge, processing the sludge to be divided into inorganic hydrous sludge and organic matter containing sludge, selecting the hydrous organic matter containing sludge for removing iron in a post-treatment process, removing the organic matter as impurity in the sludge water, pretreating biomass raw material, crushing raw material to a length of less than 3 cm, mixing organic matter water-containing sludge and the raw material in a mass ratio of 7:3, stacking the mixture in a fermentation condition, decomposing organic matter, removing nitrogen and sulfur in the organic matter, heating organic fertilizer, scattering the organic fertilizer for 24-36 hours, fermenting the mixture for 12-24 hours for 5-7 days to finish fermentation, where in each fermentation process ventilation air is circulated for 10-20 minutes, adding the biomass into the fermented mixture and then uniformly mixing, adding water (less than 30%) to the mixture, adding coal powder or machine pressing carbon black to the mixture, and refining the mixture. In the stacking step mixture, and a temperature of the mixture is controlled at more than 50 degrees C, and in the fermentation step, the temperature of the mixture is controlled to less than 80 degrees C.