The invention discloses a water quality online detection buoy station of a high-drop limit water level river, which belongs to the technical field of water quality detection. The buoy station comprises a buoy body, a probe well and a wing pendulum, wherein the major structure of the buoy body is a fully sealed hollow cylinder body; a water quality detection probe is arranged in the probe well; the probe well and the wing pendulum are the same in weight and are detachably fixed on the outer side of the cylinder body uniformly and symmetrically. In the buoy station, the wing pendulum is mounted below a water line on the side surface of the buoy body and is matched with the probe with the same weight, so that the buoy is kept to be balanced; by setting the amplitude of swing of the wing pendulum, the wing pendulum faces to the direction of water flow; when the wing pendulum is impacted by flood, the water flow and wind direction are dramatically changed, and the wing pendulum forms resistance under the influence of acting force and counter-acting force, so that the buoy body is prevented from being moved and rotated, therefore, the stability is enhanced, the balance and direction can be kept, and the problems that water quality detection equipment of a high-drop water body is high in technical requirements and is overturned easily in the prior art can be solved.