The invention discloses a real-time flying wind direction monitoring device, system and method for an unmanned aerial vehicle. The wind direction monitoring device, arranged above the body of an unmanned aerial vehicle, comprises a mounting bracket, a ball-shaped cage arranged above the mounting bracket and a flying wind vane arranged inside the ball-shaped cage. The mounting bracket comprises anairframe mounting seat below, a support rod in the middle, a universal spherical shell above and a universal spherical ball bead arranged in the universal spherical shell. The flying wind vane comprises a head, infrared transmitters, a tail wing, a horizontal lever and a vertical connecting lever. The inner wall of the body of the spherical cage is provided with a plurality of infrared receivers that match the infrared transmitters. The infrared transmitters and the infrared receivers are connected with a data storage module of the unmanned aerial vehicle. The wind direction monitoring devicecan monitor the current wind direction of the unmanned aerial vehicle in real time and provide reference for realization of better flight plans of the unmanned aerial vehicle.