NOVELTY - Method for preparing Paenibacillus polymyxa microbial fertilizer using residual sludge involves (a) preparing residual sludge culture medium by performing microwave heating pretreatment on residual sludge, (b) preparing P.polymyxa liquid seed, (c) inoculating the liquid seed into residual sludge culture medium, and feeding sterile air for culturing process, thus obtaining a liquid fermentation product, and (d) mixing fermented liquid with a high-quality organic fertilizer carrier so as to obtain a microbial fertilizer.    USE - The method is useful for preparing P.polymyxa microbial fertilizer using residual sludge (claimed).    ADVANTAGE - The method enables to prepare product which is cost-effective, and environmentally-friendly, enables to improve quality of soil environment, increase yield and quality of crops, and prevent and control various plant diseases.    DETAILED DESCRIPTION - Method for preparing Paenibacillus polymyxa microbial fertilizer using residual sludge involves preprocessing the residual sludge by selecting activated sludge of food and fermentation industrial wastewater as raw material, dehydrating the sludge, mixing the sludge with water and adjusting the concentration of the sludge to 20-60 g/l, performing microwave heating pretreatment on the obtained sludge at 90-120 degrees C for 2-20 minutes, cooling the residual sludge at room temperature to obtain residual sludge culture medium, (b) preparing liquid seed by inoculating P.polymyxa in potato liquid culture medium and culturing at 28-37 degrees C and 120-200 revolutions/minute for 24-48 hours, (c) inoculating the liquid seed in fermentation tank filled with the residual sludge culture medium, feeding sterile air into the fermentation tank, and culturing at 25-35 degrees C for 12-48 hours, thus obtaining a liquid fermentation product, and (d) mixing fermented liquid with a high-quality organic fertilizer carrier in a weight ratio of 1:5-20, uniformly stirring, and drying the mixture, until the water content is less than 30% (i) to obtain solid microbial fertilizer, packing, and storing the obtained product in shady and dry place, or (ii) to obtain product which can be directly used as liquid microbial and filling the obtained product.