Using phase change material (PCM) as an energy storage medium is one of the most efficient ways of storing thermal energy. An important organic PCM is paraffin. There are a lot of advantages of paraffin, but an undesirable property of paraffin wax is its low thermal conductivity. The main methods to enhance the thermal conductivity of PCMs are metal particles, carbon fibers, expanded graphite (EG), and nanoparticles. Thus, this kind of PCM is heat transfer unstable and easy to layering. The addition of metal particles will lead to the increase of total weight of the system and cause uneven distribution of metal particles. So, we summarized and compared the researches with the effects of the addition of carbon fibers, EG and carbon nanoparticles to paraffin-based PCMs. We find that the peak value of the thermal conductivity of the composite PCM only appeared when the mass percentage of the carbon marterial in a appropriate location. Three-dimensional thermally conductive networks is better for the thermal conductivity enhancement. And molecular interaction between CNTs and the wax makes the composite enthalpy becomes higher than pure paraffin.