Abstract: An inadequacy of paraffin, as phase transition material, is its low thermal conductivity. In order to improve the thermal conductivity of paraffin, in this experiment, the composite phase transition material was prepared using graphite with high thermal conductivity and paraffin with larger heat capacity. Its characteristic of heat transfer in the heat storage and release process is analyzed, and the affection of graphite to the heat transfer rate and phase transformation of paraffin is also studied. The results show that the admixture of graphite in the paraffin could increase thermal conductivity, reduce the fluctuation of heat transfer, with phase change time advanced obviously and phase transition time-frame shortened clearly, while little effect on phase transition temperature range is observed.