In order to design the matching high-altitude long endurance UAV power system,firstly,a certain type of fixed-wing UAV is designed with mission profiles,and a mission demand table is given to analyze the power demand under the corresponding states of different missions.Then,the mission with the largest power demand is taken as the target,and the selection of propellers and engines is carried out.Finally,the propellers are analyzed with the matching of the engines and the UAV.The results show that the selected UAV power system can meet the power demand under different flight missions.The engine and propeller selection method based on the structural and kinematic parameters of the UAV and the UAV power system matching design method based on the thrust balance and power balance can effectively guide the selection of the UAV power system as well as the matching of the power between the UAV,the engine and the propeller.The results of the study provide a method for fixed-wing UAVs to match the power system according to the requirements to fulfill their flight missions.