Myristic acid/expanded graphite (MA/EG) composite phase-change material (CPCM) was prepared by absorbing liquid MA (as the PCM) into EG (as the supporting material). Its chemical structure, microstructure, and thermal properties were characterized and studied. In the MA/EG CPCM, the largest mass content of MA was 93.5% by using the diffusion-exudation circle method for the first time. Fourier transform infrared spectroscopy (FTIR) analysis indicated that the MA and EG were a pure physical mixture of which the structure does not change, and they undergo no chemical reaction. Differential-scanning-calorimetry (DSC) analysis results showed that the melting and freezing temperatures of the MA/EG CPCM were 53.3 and [Formula: see text], respectively, and the melting and freezing latent heats were 189.5 and 187.8 J/g, respectively. After several heat-cycle accelerations, the material still had good thermal-energy-storage effect. MA/EG CPCM thermoconductivity was greatly enhanced after adding EG, and the results of thermal-storage/-release experiments indicated that the thermal-storage and -release ratios of the MA/EG phase-change unit was greatly improved when compared with that of MA. These results indicated that the MA/EG CPCM was a suitable low-temperature thermal-energy-storage material.