In this paper, different particle sizes of kaolin were employed to incorporate paraffin via vacuum impregnation method. The paraffin/kaolin composites were characterized by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeter (DSC) and Thermogravimetry (TG). The results showed that the paraffin/kaolin composite with the largest particle size of kaolin (K4) has the highest thermal conductivity (0.413 W/(m K) at 20 degrees C) among the diverse composites. The latent heat capacity of paraffin/K4 is 119.49 J/g and the phase change temperature is 62.4 degrees C. In addition, the thermal properties and thermal conductivities of paraffin/K4 with different mass fraction of K4 (0-60%) were investigated. The thermal conductivities of the composites were explained in microcosmic field. The phonon mean free path determines the thermal conductivity, and it can be significantly affected by temperature and the contact surface area. The leaks, thermal storage and release properties of pure paraffin and paraffin/kaolin composites were investigated and the composites presented good thermal stabilities. (C) 2016 Elsevier Ltd. All rights reserved.