The invention discloses a preparation method and an application for a filling material applied to a combined triple-effect ecological floating bed. The invention is to improve water purifying abilityand nutrient supplying performance of a substrate in a conventional ecological floating bed. The filling material is prepared by compounding a hard solid filling material A and a polyurethane sponge soft filling material B. The preparation method comprises the following preparation processes: batching, mixing and granulating, drying, curing, cooling, and compounding and foaming. According to the invention, used raw materials are low in price; the manufacturing method is simple; and an obtained filling material has the advantages of large specific surface area, high porosity, good microbial biofilm-forming performance, strong nitrogen and phosphorus removal abilities, etc. The filling material is applied to the combined triple-effect ecological floating bed, and can greatly improve removalcapacity of a ecological floating bed device to nitrogen and phosphorus nutrient elements in a water body; and the filling material has nitrogen-phosphorus sustained-release properties, can provide astable nutrient supply environment for the growth of crops, and is extremely applicable to in-situ purification treatment of a eutrophic water body, specifically to purification of a water body with non-point source pollution in a farmland.