High-precision integrated star sensors have a high pointing accuracy and are highly sensitive to temperature changes. The external heat flow in near-Earth orbits is complex and variable. The comprehensive factors of the integrated structure and the concentration of the internal heat source not only lead to difficulty in the heat dissipation design, but also make it difficult to guarantee the pointing accuracy of the lens directly affected by the internal heat source. First, combined with the orbital parameters, the installation layout provides the average absorbed external heat flux of the star sensor. Subsequently, by analyzing the working conditions of the external and internal heat flows, a thermal design method combining passive and active thermal control is adopted, and the position and size of the heat dissipation surface of the star sensor are designed and calculated. Finally, thermal analysis and verification are performed using thermal simulation software according to the orbital environment and thermal control measures. The simulation results show that the installation flange temperature is 19.82?20.10℃ , the axial temperature difference of the lens is less than 2.23℃ , the circumferential temperature difference is less than 0.48℃ , and the circuit box temperature is 19.10?23.49℃ , which meets the thermal control index. The stable working conditions of the extremely highprecision star sensor are ensured by a reasonable thermal control design, and the thermal design of the star sensor is reasonable and effective.