Abstract: The missile-borne microwave processing unit has many channels and complex system functions. In the closed and harsh bomb chamber environment, how to dissipate the internal high-power chip to ensure the long-term service reliability of the equipment has been a key issue of concern. In this paper, a design method of phase change heat storage module is proposed based on the design requirement of high-power microwave processing unit. Through thermodynamic calculation, the strength reliability of phase change structure and the heat absorption capacity of selected phase change material are verified. According to the simulation results, the junction temperature of the high-power chip is lower than the allowable junction temperature of the chip after 700s of continuous working and heating at 70℃, and has a certain safety margin. The phase-change heat storage module can significantly reduce the temperature of the chip mounting surface, and provide effective technical support for the equipment to adapt to the environmental requirements and provide reliable and stable service status.