To　overcome　the　challenges　of　low　thermal　conductivity　and　leakage　of　fatty　acid　based　phase　change　materials　(PCMs),　a　high-efficiency　form-stabilized　composite,　with　the　use　of　styrene　ethylene　butylene　styrene　(SEBS)　as　structure　material,　was　prepared　and　investigated　in　this　work.　The　myristic　acid　(MA)　was　used　as　PCM　and　graphite　was　employed　as　thermal　conductivity　enhancer　to　improve　composite　thermal　conductivity.　A　series　of　characterizations　were　performed　to　investigate　the　composite　microstructure,　chemical　compatibility　and　thermal　properties.　Furthermore,　the　thermal　conductivity　and　mechanical　strength　enhancement　of　the　composite　were　evaluated　by　dispersing　of　high　density　polyethylene　(HDPE).　The　results　showed　an　excellent　chemical　compatibility　in　the　composite.　The　MA　can　be　uniformly　dispersed　in　the　SEBS　matrices　and　15　wt%　SEBS　endowed　the　composite　with　the　capacity　to　maintain　structure　stabilization.　The　Differential　Scanning　Calorimetry　and　Laser　Flash　Analyser　results　revealed　that　the　MA/SEBS/graphite　composite　with　a　mass　ratio　of　85:15:10　presented　a　constant　melting　temperature　around　53　degrees　C,　high　latent　heat　of　150.33　kJ/kg　and　high　thermal　conductivity　of　0.655　W/m.K.　The　composite　thermal　conductivity　and　mechanical　strength　can　be　further　enhanced　by　adding　of　HDPE　and　a　loading　of　5　wt%　HDPE　achieves　the　enhancement　of　the　composite　thermal　conductivity　and　mechanical　strength　respectively　by　25.4%　and　16.4%.