Method for preparing fertilizer by utilizing sludge

The invention relates to a method for preparing a fertilizer by utilizing sludge. The method comprises the following steps: domesticating domestic sludge into anaerobic sludge: concretely standing thedomestic sludge for two days or more, and carrying out fermenting to obtain anaerobic sludge for later use; and adding 20-30% of anaerobic sludge into the domestic sludge, uniformly carrying out mixing by 10-20 minutes, then carrying out standing for 24-48 hours, introducing carbon dioxide with a mass percent of 5-10% of the mass percent of the sludge, adding auxiliary raw materials, continuouslyadding 20-30% of oxygen-free sludge (based on the original domestic sludge), uniformly carrying out stirring, and carrying out piling fermentation at 15-50 DEG C for 15-20 days to obtain the fertilizer. After the fertilizer is used, cultivated apples are bigger than apples in past years and have sufficient moisture; the size and specification of the cultivated potatoes are consistent; rice grainsof 2-3 qian are achieved i