The invention belongs to the technical field of environmental protection, and particularly relates to a floating plant treatment device for a eutrophic water body. The following scheme is proposed nowaiming at the problems that algae are small and fragile, are prone to be broken when fishing, and are not fished clean. The floating plant treatment device includes a hull, wherein the bottom of thefront end of the hull is connected with a supporting rod through bolts, the other end of the supporting rod is connected with a sleeve through bolts, and the bottom end of the inner part of the sleeveis hinged to a connecting rod, and the top of the connecting rod is hinged to a collecting cover. According to the floating plant treatment device, a method of using the collecting cover to collect plants floating on water surface cannot produce noise, the range of collection is wide, at the same time, floating plant spreading around cannot be caused, the collection effect is good, an arc-shapedbulge is arranged on the inner surface of a drainage ring, floating plant sticking and staying can be avoided, the collection speed of floating plants is further improved, device loading caused by floating plant accumulation can be reduced, the amount of treating floating plants by the device for one time is increased, and operation time is prolonged.