NOVELTY - Preparation of fermented nutritional agent for soil, involves (a) drying leftover sludge from sewage treatment plant by spreading sludge and drying sludge naturally to obtain dried sludge materials, growing mushroom in suitable substrate, crushing the substrate, mixing crushed substrate with dried sludge materials, adding culture liquid to substrate-sludge mixture and fermenting mixture to obtain fermented mixture, (b) adding fermented mixture into fermenting device, and (c) carrying out aerobic-anaerobic alternative fermentation.    USE - The method is useful for preparing fermented nutritional agent for soil.    ADVANTAGE - The method enables preparing less toxic nutritional agent which improves nitrogen and phosphorus content in soil, and ferments urban garbage in large scale level and thus decreases risk of eutrophication. The method is environmentally-friendly as the waste materials are recycled.    DETAILED DESCRIPTION - Preparation of fermented nutritional agent for soil from sludge, involves (a) drying leftover sludge from sewage treatment plant by spreading the sludge and drying the sludge naturally for reducing the water content to 75% to obtain dried sludge materials, growing mushroom in suitable substrate, crushing the substrate, mixing the crushed substrate with the dried sludge materials in a ratio of 1:1, adding culture liquid to the substrate-sludge mixture and fermenting the mixture at 70 degrees C for 5-7 days to obtain fermented mixture, where the dried sludge, substrate and the culture liquid are in the ratio of 1:1:1, and the moisture content of the fermented mixture is 60-65%, (b) adding the fermented mixture into fermenting device, where the amount of fermented mixture added into the device is 4/5 the amount of mixture, which is 5/6 the volume of device, and covering the device using lid, and (c) carrying out aerobic-anaerobic alternative fermentation by supplying aeration for 5 minutes at the rate of 1.4-2.8 m3/hour, stopping the aeration for 30 minutes and repeating the same for 5 days and carrying out anaerobic fermentation for 3 days.