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 heat of 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 calculation verification and simulation analysis, a phase change heat storage module with reliable structural strength and heat absorption capacity meeting the requirements is obtained. According to the simulation results, the junction temperature of the high power chip is lower than the allowable junction temperature of the chip after 700 s of continuous working at an ambient temperature of 70 ℃, and has a certain safety margin. After working for about 100 s, this phase change heat storage module can temporarily slow down the temperature rise rate of the chip, which can provide effective technical support for the equipment to adapt to environmental requirements and maintain a reliable and stable service state.