Aiming to improve the endurance of solar-powered UAV in low altitude in a mission cycle, a high-efficiency propeller design method is proposed. According to the flight span curve of the solar-powered UAV, the climb and main cruise altitudes are selected as the design points. Firstly, based on the Betz minimum energy loss design criteria and the strip theory and its reverse derivation, the chord length and pitch under each design point are calculated Angular distribution, and then assign weights to the calculation results of each design point according to the flight span curve to obtain the final design chord length and pitch angle distribution. Finally, based on the CFD numerical simulation technology, the designed propeller is simulated and calculated on the basis of the verification algorithm. The results show that compared with the conventional propeller, the efficiency of the propeller designed in this paper is within the flight envelope of the entire mission cycle under the allowable power range. The interior has been significantly improved to meet the design requirements.