FY-4 is a geostationary three-axis stable platform meteorological satellite. The radiation imager loaded on it is affected by the dramatic daily and periodic changes of the external heat flow. The temperature of key components such as the scanning mechanism and the main optical system fluctuates over 40°C per day. How the optical and supporting structures adapt to severe environmental temperature changes and ensure good image quality is an international problem in the design of remote sensing instrument systems for geostationary triaxial stabilization platforms. The matching design of various materials and the adoption of appropriate supporting structure forms are good strategies to avoid and reduce the deformation of the optical machine and the degradation of imaging quality caused by large temperature fluctuations. The on-orbit data indicates that the radiation imager overcomes the adverse effects of large temperature difference between day and night. The diffuse plaques of sensitive stars cover only one pixel, and the noon and midnight results are not much different.