The invention discloses an environment-friendly water purifier, preparation and using methods thereof. The water purifier is prepared by mixing a flocculating agent, a metal-chelator and microbes; under the combined action of the three ingredients, the purification effect of a water body can be strengthened, the water body quality can be remarkably improved, the water body becomes clear, odor can be eliminated, the hardness of the water quality can be reduced, the dissolved oxygen can be increased, the contents of ammonia nitrogen and nitrate nitrogen of the water body can be reduced, heavy metal ions can be reduced, pathogenic bacteria can be reduced, suspended matters and harmful algae in the water can be reduced, diseases of aquatic animals and plants can be reduced, degradation of pollutants in the water can be accelerated, and the aquatic ecological development is healthy and sound. The water purifier does not contain aluminum, iron, chlorine, heavy metal ions or other harmful substances, is safe, environment-friendly and healthy, has a remarkable effect of purifying sewage in the agriculture, animal, husbandry and fishery industries, domestic sewage and industrial sewage, and is of important meaning for environmental protection and human health protection.