The invention discloses a water body clarifying agent capable of improving the water body self-purifying capacity.The water body clarifying agent is prepared from, by weight, 24-25 parts of silkworm excrement, 13-15 parts of molasses, 1.4-1.6 parts of a nitrifying bacterium microbial agent, 3.3-3.5 parts of a bacillus subtilis microbial agent, 2-3 parts of sodium polyacrylate, 3-4 parts of ferric citrate, 0.4-0.5 part of microcrystalline cellulose, 65-66 parts of sunflower heads, 2.1-2.3 parts of ferroferric oxide powder, 25-27 parts of a ferrous oxalate solution with the concentration of 0.1 mol/L, an appropriate of an acetic acid solution and an appropriate of water.According to the water body clarifying agent, the community structure of beneficial bacteria in a water body is enriched through the microbial agent additives, therefore, a fermentation reaction of protein in excessive quantity of organic substances in the water body is achieved, and harmless decomposition of sludge is achieved; in addition, secreted floccules in the microbial metabolism process and contaminants in the water body form molecular groups to be settled, and then the water body self-purifying purpose is achieved.