The invention discloses a large on-water floating structure which comprises multiple lower-portion floating bodies, upper-portion structures and middle connecting structures. Each lower-portion floating body comprises multiple dispersedly arranged strip-shaped floating bodies, the floating bodies are spaced for a certain distance, the sum of water discharging volumes of the floating bodies is greater than that of the floating structure in a whole full-load state. Each middle connecting structure at least comprises multiple connecting structures in the first direction, the first direction is intersected with a horizontal plane, the single strip-shaped floating bodies corresponding to the connecting structures in the first direction are connected with three or more mutually spaced structures, and the cross section widths of the middle connecting structures in the horizontal direction are smaller than the widths of the corresponding strip-shaped floating bodies. The on-water floating structure is wholly in an ultra-flat shape. The large on-water floating structure has a wave height nonlinear response characteristic, can reduce wave load, can achieve ultra large scale, has excellent wave resistance, has structural integrity and stable height redundancy and has the characteristics of no disassembly and no capsizing and sinking under the accident conditions such as collision, reef striking and stranding, and the safety of the floating structure and the life safety of persons on the structure can be ensured.