Mg-Al-CO3-Hydrotalcite (HT) was prepared via hydrothermal synthesis method in this paper. Then the HT was organically modified. The composite PCM was prepared with the organic HT and paraffin via the liquid intercalation. The interlayer groups of HT were investigated using a Fourier Transform Infrared Spectroscopy (FTIR) before and after modification. The microscopic structure of the organic HT/paraffin composite PCM was characterized using a Scanning Electron Microscope (SEM). The thermal properties were measured using a Differential Scanning Calorimeter (DSC) and a thermal constant analyzer. The results showed that the HT prepared via the hydrothermal synthesis had single crystal phase and high crystallinity. The layer spacing of the organic HT was expanded. The intercalation rate of paraffin was 25.9 wt% in the organic HT. The phase transition temperature and the phase change enthalpy of the organic HT/paraffin composite PCM were 26.2 degrees C and 29.8 J/g, respectively. (C) 2015 Elsevier Ltd. All rights reserved.