Expermental results and analysis of long-term thermal stability of capric acid/myristic acid molecular alloy as phase change material(PCM) are presented.Phase change temperature and phase change heat of the phase change materials,which have undergone 56,112,200,400 and 710 accelerated thermal cycles,were measured by differential scanning calorimetry(DSC) technique.The test results indicate that the phase change temperature and phase change heat of the phase change materials are not much changed after large number of thermal cycles.