The development of solar-powered unmanned aerial vehicles (UAVs) primarily focuses on enhancing the efficiency of the propulsion system to minimize energy consumption during the conversion of valuable solar energy. However, due to the unique nature of UAV propulsion systems, there is limited cross-reference ability among existing solar-powered UAV systems. This paper proposes an integrated design approach for the propulsion system and UAV structure. Based on this approach, an overall design is conducted for the solar-powered UAV, including initial design goals and performance parameters. Aerodynamic layout design and performance estimation are carried out, and a prototype is fabricated and assembled for flight testing validation. The results demonstrate the significant importance of this approach in improving the efficiency of the solar-powered UAV propulsion system.