The invention discloses an ecological dam protecting material capable of absorbing such pollutions as nitrogen and phosphorus in water and a preparation method of the material. The material, adhering to the core of water supply plant sludge, natural zeolite, ordinary Portland cement and plant foaming agent, modifies the water supply plant sludge and the zeolite to absorb nitrogen and phosphorus elements as well as organic substance in water, thus constructing an ecological system growth matrix environment, so as to realize self-purification function of the water; the ordinary Portland cement and the plant foaming agent, as accessories, serve as controlling honeycomb structure, water permeability, gas permeability and mechanical performance of the material, thus constructing a 'nutrient element absorption and immobilization-biological reproduction-water purification' ecological structure. The material has the advantages of being simple in proportion, low in investment, environment-friendly and efficient, and has advantages on honeycomb structure, water permeability, gas permeability, mechanical performance and the like. The material disclosed by the invention not only guarantees communication and slope protection functions among air, water and soil of river bank slope, but also can be used for improving the surrounding atmospheric environment, thus generating an excellent landscape effect.