We prepared and characterized a form-stable composite phase change material (PCM) with higher thermal conductivity. Capric acid(CA)-myristic acid(MA) eutectic as core, poly-methyl methacrylate (PMMA) as supportive matrix and modified graphite (MG) powders serving as the thermal conductance improver were blended by bulk- polymerization method. The composite PCMs with different MG mass fraction (2%, 5%, 7%, 10% and 15%) were characterized by FT-IR, SEM, DSC technique and mechanical tests. Thermal conductivities of the composites were measured by transient hot-wire method. The results indicate that MG powders have been successfully inserted into the CA-MA/PMMA matrix without any chemical reaction with each other. The MG/CA-MA/PMMA composites maintain good thermal storage performance while the thermal conductivity has been enhanced significantly. The composite PCM added with 15 wt% MG powders increases approximately as 195.9% in thermal conductivity. Moreover, the thermal conductivity improvement of the composite PCMs is also verified by the melting-freezing experiment, which is profitable for the heat transfer efficiency in latent heat thermal energy storage system. Capric acid (CA) -myristic acid (MA) eutectic as core, poly-methyl methacrylate (PMMA) as supportive matrix and modified graphite (MG) The composite PCMs with different MG mass fractions (2%, 5%, 7%, 10% and 15%) were characterized by FT-IR, SEM, DSC The results indicate that MG powders have been successfully inserted into the CA-MA / PMMA matrix without any chemical reaction with each other. The MG / CA- MA / PMMA composites maintain good thermal storage performance while the thermal conductivity has been significantly enhanced. The composite PCM added with 15 wt% MG increases in polymer as much as 195.9% in thermal conductivity. Moreover, the thermal conductivity impr ovement of the composite PCMs is also verified by the melting-freezing experiment, which is profitable for the heat transfer efficiency in latent heat thermal energy storage system.