Abstract: The missile-borne electronic equipment may experience an acute temperature rise in the short-time high power consumption mode, with the risk of failure. In order to solve this problem, some kinds of PCM heat sinks are studied by different design methods and in different processing paths. Through thermal simulation, the carbon-based special paraffin composite PCM is shown to be lighter and with better heat dissipating capability. Then, a graphite-based special paraffin composite PCM is precisely designed and adopted to a newly-developed high heat flux module. The thermal simulation results show that the heat dissipation performance can meet the technical requirements. After that, a thermal test under the same condition is conducted, and the results are compared with the simulation results . The method and the results of this paper can be used in the thermal design and the thermal management using the PCM heat sink under rigorous conditions.