The invention relates to a special microorganism strain for processing steel slag, vinegar residues and weathered coal and a preparation method thereof. The microorganism strain comprises hansenula anomala, film press hansenula, pichia farinose, saccharomyces cerevisiae, geotrichum candidum, bacillus subtilis withered grass subspecies, bacillus licheniformis, bacillus megaterium, lactobacillus acidophilusis and streptomyces microflavus in the mass ratio of 2:2:2:2:1:5:3:2:1:4. The preparation method comprises the steps of microorganism selection, activation, one-class expansion, second-class swinging bed amplification, carrier adsorption, preparation, low-temperature drying, detection, metering and packaging. The invention can harmlessly process the steel slag, vinegar residues and weathered coal, neutralizes the strong alkalinity of the steel slag by utilizing the organic acid generated in the process of fermentation, forms an organic acid metal complex, reduces the fixation of nutrients, improves the effective utilization ratio of the nutrients, efficiently utilizes organic sources, such as steel slag, vinegar residues, weathered coal, and the like, and reduces environmental pollution.