With the increasing lifespan of satellites, the design of solar arrays, which serve as the direct energy source for spacecraft, requires more refined considerations. This study focuses on the key characteristic parameters of the commonly used triple-junction gallium arsenide solar cells. By processing and analyzing on-orbit data from a specific satellite, a reliability power function model is established to assess the lifetime and reliability of the solar arrays. The study achieves the prediction of reliability at a given lifespan and the determination of operational lifespan under a specific reliability level based on the fitted model.