The invention discloses a small high-load unmanned aerial vehicle for agricultural spraying and application of the small high-load unmanned aerial vehicle. The small high-load unmanned aerial vehicle comprises driving motors, a propeller crossbeam, a vehicle body, an accumulator and control system, a propeller steering device, a high-pressure vessel, undercarriages, propellers, spraying heads and a high-pressure valve. The counterforce of sprayed objects is utilized to assist the propellers to generate lift force during flying, so that effective load of the unmanned aerial vehicle is increased, working efficiency is improved, duration of flight can be increased, flight attitude adjustment is facilitated, and feasibility of application of the small unmanned aerial vehicle to spraying of large-area farmland is improved.