The invention provides a device for measuring the coverage degree of large aquatic plants, and belongs to the technical field of measuring devices.The device for measuring the coverage degree of the large aquatic plants comprises a remote control ship body, a transverse plate is fixedly connected to the upper surface of the remote control ship body, a through hole is formed in one side of the transverse plate, and a movable rod is movably connected to the interior of the through hole; a first measuring instrument is fixedly connected to one end of the movable rod, a sliding groove is formed in the upper surface of the transverse plate, and a sliding block is slidably connected into the sliding groove. Through arrangement of a movable rod, a first threaded rod, a threaded ring, a first motor, a rotating shaft and a vertical plate, during use, a remote control ship body is firstly controlled to move to a to-be-detected area, and then the first motor is started to rotate the first threaded rod, so that the threaded ring moves forwards on the first threaded rod after being subjected to the acting force of the first threaded rod; at the moment, the vertical plate horizontally rotates on the threaded ring to push the connecting block, so that the movable rod is contracted, control is convenient, and the position of the first measuring instrument can be freely adjusted.