In this paper, an analysis of thermal performance is carried out for heat sinks with a graphite sheet. At first, an numerical simulation is performed by using the commercial code COMSOL Multiphysics 4.2a to explore the effects of material property on the heat transfer behavior of the heat sink. Then an experiment is performed to measure the thermal performance of the heat sink. After this, the results of experimental measurements are compared to those of the simulation ones. It can be summarized that the addition of a graphite sheet has the effect to enhance the thermal performance of the heat sink.