Composite phase change materials (PCMs) based on reduced graphene oxide/expanded graphite (rGO/EG) aerogel were prepared by hydrothermal self-assembly and impregnation method. The morphology, chemical structure, thermal properties, and shape-stability of the composite PCMs based on rGO/EG aerogel were examined. The results show that rGO sheets form a three-dimensional (3D) network structure and EG particles are attached to rGO sheets and uniformly interspersed in the aerogel. The oxygen-containing functional groups remaining in rGO/EG aerogel promote heterogeneous crystallization of paraffin, leading to increased latent heat. The 3D thermally conductive pathway provided by rGO/EG aerogel improves the composite PCM's thermal conductivity up to 0.79 W center dot m(-1)center dot K-1, which is about 4 times of that of pure paraffin. The leakage of composite PCMs is remarkably improved at very high percentage of paraffin. Simulative light-thermal experiments reveal that the composite PCMs have the ability of conversion and storage of light-thermal energy. In short, 3D network structure of rGO, with the aid of EG, endows the composite PCMs with improved thermal properties, good shape-stability, and light-thermal storage performance.