Abstract: Due to the complex thermal environment in space, the attitude measurement results by the star sensor exhibit low-frequency error of boresight axis thermal drift during the orbital period. Therefore, thermal design and thermal stability test verification for star sensor are required. In this article, an overall scheme for the thermal stability test of the star sensor was proposed, and a thermal stability test system was established. According to the vacuum thermal environmental testing specifications for spacecraft, the criteria and conditions for thermal stability test of star sensor were presented. A control method for the test system error was put forward and a thermal stability test was carried out for a star sensor. The test results indicate that the boresight axis thermal drift of the star sensor is 0.114 (")/℃, which meets the reguirements of the design index. The effectiveness of the star sensor thermal design is experimentally verified.