The invention discloses a three-dimensional floating bed and sinking bed combined type river water purifying device which comprises a reinforced ecological floating bed system and an ecological sinking bed system. The ecological floating bed system comprises emergent aquatic plants, filler and clams, wherein a biological film formed by a heterotrophic nitrification and aerobic denitrification bacterium hanging film is cultivated on the filler. The ecological sinking bed system comprises submerged plants, filler and ceramic particles, wherein a biological film formed by a humic acid reduction bacterium hanging film is arranged on the filler. The removal rate of COD in a water body can reach 60-80%, the nitrogen removal rate can reach 50-60%, the phosphorus removal rate can reach 20-30%, and the removal rate of humic acid and other large molecules difficult to degrade reaches 50-60%; by means of a float, the device can float up and sink down in water; due to the three-dimensional type structure and the adjustable structure, the water purification of a deep river bed is facilitated; in winter, ceramic particles can continuously have an adsorption effect so that water can be purified. A continuous effect is achieved for the water body of a river way, the ecological system of the river way is improved, and the self-purification capacity of the water body is restored.