A submerged water quality improving device of combined ecological floating floor belongs to the technical field of ecological environment engineering, comprising a floating plate, a convex floating block, a planting basket, planting basket filler, floating floor plant, artificial float grass, and the like; the convex floating block is fixed above the floating plate; the planting basket is arranged in the planting basket hole of the floating plate; the planting basket filler is arranged in the planting basket; the floating floor plant is cultivated in the planting basket filler; and the artificial float grass is hung under the floating plate. The floating plate is internally provided with a reinforcing rib; and the convex floating block is made into biomimetic shape. After the floating plate and the convex floating block are submerged, the total buoyancy is more than the sum of the total weight of the floating plate, the planting basket, the planting basket filler, the artificial float grass and the float convex floating block, and 1.5 times of weight of the floating floor plant; and the convex floating block emerges from the water. The carrier is simple, convenient and economic, and has high intensity, good durability and reliable planting; the floating plate is submerged so as to achieve the effect of natural water ecological landscape and engineered effect of water quality improvement.