A buoy position monitoring method includes a buoy positioning step, an unmanned aerial vehicle receiving step and an unmanned aerial vehicle flying step. In the buoy positioning step, a plurality of buoys are put on a water surface. Each of the buoys is capable of sending a detecting signal. Each of the detecting signals is sent periodically and includes a position dataset of each of the buoys. In the unmanned aerial vehicle receiving step, an unmanned aerial vehicle is disposed on an initial position, and the unmanned aerial vehicle receives the detecting signals. In the unmanned aerial vehicle flying step, when at least one of the buoys is lost, the unmanned aerial vehicle flies to a predetermined position to get contact with the at least one buoy that is lost.