In order to solve the on-orbit temperature drift problem of TDI-CMOS sensors and further improve the imaging quality of the space camera, it is necessary to control the temperature rise of the sensor chip during on orbit imaging, and optimize the heat transfer path of the focal plane assembly by using a phase change energy storage device. Firstly, the simulation and experimental boundary conditions are determined based on the thermal flow environment of the track and the working characteristics of the focal plane assembly. The existing focal plane assembly structure is used for modeling, simulation analysis and thermal testing to obtain the temperature results of each part before optimization. Then, based on the existing structure, thermal control optimization design is carried out to study the effect of different heat transfer paths on the temperature improvement of CMOS sensors, and a thermal design scheme of the focal plane assembly supplemented by a phase change energy storage device is determined, Finally, the thermal equilibrium test of the focal plane assembly is carried out to verify the correctness of the design scheme. The experimental results show that the enhanced heat transfer method combining the pin heat dissipation scheme and side heat dissipation can meet the temperature rise requirements of CMOS sensors within 5 ℃ during operation, and the DN value change is less than 0.2%. The optimized scheme effectively improves the imaging quality.