Hα solar space telescope has the functions of solar spectral imaging and full-disk solar imaging, which is multi-functional and highly integrated. It is located inside the satellite payload cabin, its on-orbit attitude is changeable, and it has the working mode of continuous observation, which leads to the harsh thermal environment of focal plane assembly and electric boxes, and puts forward higher requirements for thermal design. Through the integrated design of the payload with satellite and the reasonable layout of the telescope's structure, the radiation heat dissipation channel was reserved in the satellite payload cabin near the camera. The heat dissipation surface was reasonably designed to export the working heat consumption quickly, ensuring that the temperature of each component met the index. By building the thermal equilibrium test platform, the thermal analysis, thermal equilibrium test and in-orbit data was compared under high and low temperature conditions. The maximum temperature difference of each electric box under the same working condition was ≤4 ℃, the correctness of the thermal design was verified, which ensured the normal operation of Hα solar space telescope in complex space environment. It has certain reference significance for the thermal control design of such space solar telescope.