Hydrated salt of aluminium potassium sulfate dodecahydrate (APSD)/expanded graphite (EG) form-stable composite phase change material (PCM) has been prepared. Hydrated salt of aluminium potassium sulfate dodecahydrate used as the PCM was firstly modified by using nucleator and thickener with the aiming at solving the supercooling and phase separation. Sulfurized EG is selected as supporting matrix to overcome leakage and low thermal conductivity of MAPSD. Furthermore, hydrophilic and hydrophobic groups on the surface of the expanded graphite is oriented by carrying out titanate coupling agent, which could restrict the volatilization of crystal water and solve the poor cyclic stability problems of APSD. The thermal performance of modified APSD (MAPSD) and modified EG (MEG)/MAPSD composite PCMs are tested and analyzed by using Differential Scanning Calorimeter (DSC), Hot Disk Thermal Constant Analyzer and a small-scale experimental device. The DSC analysis showed that the melting enthalpy of form-stable composite PCM containing 80 wt% APSD and MAPSD are 473.52 and 641.75 J/g, and their corresponding melting points are 84.39 and 84.34 degrees C, respectively. The 100 times melt-freeze cyclic tests revealed that the mass of MAPSD decreases by 45.57%. However, the mass of MEG/MAPSD composite PCMs decreases by only 7.91% when the sample density (rho) of 900 kg/m(3) and mass fraction of MEG with 20%, which could still maintain its original shape perfectly without any change. What's more, the effective thermal conductivity of MEG/MAPSD composite PCM (6.157 W/(m.K)) is about 11 times higher than that of pure APSD (0.55 W/(m.K)) and Agari-Uno model is used to predict the thermal conductivity of composite PCMs with different MEG contents. The average deviation is only 3.91% between experimental and predicted value. All the results indicate that the form-stable MAPSD/MEG composite PCMs can be considered as high-performance latent heat storage materials and the great potential for practical application in solar thermal utilization. (C) 2019 Elsevier Ltd. All rights reserved.