Abstract: Some electronic equipment works in short time with high heat flux, which will cause a steep temperature rise that may even lead to equipment failure. In order to solve this problem, the expanded graphite/higher alcohol composite phase change material (PCM) is adopted in a high heat flux module. A comparison between PCM and Al as the heat sink material is made through simulation. It is shown that the PCM heat sink enjoys a superior thermal performance over the Al heat sink in the non-active cooling platform. A thermal experiment under the same condition is conducted to verify the superior thermal performance of the PCM and to make comparison with the simulation results as well. It is shown that both results have the same trend of temperature variation, but specific temperature change rates are observed for different phase change temperatures. The difference between the experiment and the simulation is analyzed, and the results may provide a basis for the thermal design and management using PCM as the heat sink under rigorous conditions.