Aiming at the thermal characteristics of space solar telescope with long working time and harsh working environment, the thermal design of space solar telescope frame and guiding telescope under extreme working conditions was carried out. Through the finite element simulation analysis and thermal equilibrium test under high and low temperature conditions, the thermal analysis and thermal equilibrium test results of the frame and the guiding telescope were compared. The temperature was controlled at 22 °C, and the temperature fluctuation of each component under the same condition was less than 1 °C, which verified the correctness of the thermal control design. At the same time, the power difference between the finite element simulation of the frame and the guiding telescope and the thermal equilibrium test was 1.2 W at high temperature and 0.8 W at low temperature. The simulation analysis is consistent with the thermal equilibrium test, and the analysis is correct and effective, which ensures the normal operation of the telescope under complex working conditions. It provides a theoretical basis for improving the reliability and thermal design optimization of the space solar telescope module and solar tracking optical system.