Abstract: The thermal test is one of the important steps in the development of optical remote sensors. It aims at validating the thermal design for the sensors concerning the adaptability under the flight environment, the working state of the onboard instruments, and the matching between various subsystems. The accuracy of the simulated temperature boundary has a direct influence on the effectiveness of the test. This paper discusses the technology for the proper simulation of the temperature boundary. The technical issues that should be paid attention to in the design process are discussed, a method is proposed to improve the temperature uniformity at the temperature boundary of the mechanical installation structure for the optical remote sensor.