Abstract: The lightweight nature, compactness, and stringent temperature requirements for optical components pose challenges to the thermal control design of inter-satellite laser communication terminals. A fixed co-orbital terminal was chosen as the research object, and a comprehensive thermal control design process was conducted from thermal transfer analysis to thermal control scheme, considering the influence of platform and space environment factors on the terminal. Based on the unique structural characteristics of the co-orbital terminal, a flexible radiator was designed, combined with active heating circuits, significantly enhancing the terminal’s thermal control adaptability across different orbital networks. Ground and on-orbit verification results indicate that the designed thermal control scheme ensures the on-orbit temperature fluctuation of the optical system of the co-orbital inter-satellite laser communication terminal to be within ±0.4 ℃. This research provides a simplified design method for the thermal control system of laser communication terminals, which can be used as a reference for subsequent thermal control design of related terminals.