A large-load unmanned aerial vehicle (UAV) for plant protection with adjustable spraying swath and pesticide application amount is provided, relating to the technical field of pesticide application of unmanned aerial vehicles. The large-load unmanned aerial vehicle for plant protection comprises a large-load unmanned aerial vehicle, a pesticide box, a variable pesticide application system, and adjustable spraying swath mechanisms, wherein the pesticide box is fixed to landing gears of the unmanned aerial vehicle and is positioned below a control platform of the unmanned aerial vehicle; the adjustable spraying swath mechanisms are arranged on the landing gears, the variable pesticide application system is connected with the pesticide box and the adjustable spraying swath mechanisms, the variable pesticide application system and the adjustable spraying swath mechanisms are electrically connected with the control platform, and the control platform is in communication connection with a remote control handle.