The utility model provides a simple seedling airing device for floating seedlings, which comprises at least one cuboid hollow tray airing frame, and the cuboid hollow tray airing frame comprises a plurality of three-way elbows and telescopic connecting rod components. The three-way elbows are sequentially arranged at the octagonal positions of the cuboid hollow tray airing frame. The telescopic connecting rod assemblies are detachably connected with the corresponding three-way elbows respectively, so that the cuboid hollow tray airing frame is formed. The tray is convenient to air, store and stretch, so that the practicability is improved, and popularization and application are facilitated.