In　order　to　solve　the　problems　of　low　thermal　conductivity　and　easy　liquid　leakage　of　a　stearic　acid　(SA),　the　composite　phase　change　material(PCM)　was　prepared　by　adding　boron　nitride　(BN)　and　expanded　graphite　(EG)　to　melted　SA,　and　its　thermal　conductivity,　crystal　structure,　chemical　stability,　thermal　stability,　cycle　stability,　leakage　characteristics,　heat　storage/release　characteristics,　and　temperature　response　characteristics　were　characterized.　The　results　showed　that　the　addition　of　BN　and　EG　significantly　improved　the　thermal　conductivity　of　the　material,　and　they　efficiently　adsorbed　melted　SA.　The　maximum　load　of　SA　was　76　wt.　%　and　there　was　almost　no　liquid　leakage.　Moreover,　the　melting　enthalpy　and　temperature　were　154.20　J　•　g　−　1　and　67.85°C,　respectively.　Compared　with　pure　SA,　the　SA/BN/EG　composite　showed　a　lower　melting　temperature　and　a　higher　freezing　temperature.　In　addition,　when　the　mass　fraction　of　BN　and　EG　was　12　wt.　%,　the　thermal　conductivity　of　the　composite　was　6.349　W　•　m−1　•　K−1,　which　was　18.619　times　that　of　SA.　More　importantly,　the　composite　showed　good　stability　for　50　cycles　of　heating　and　cooling,　and　the　SA　/　BN　/　EG-12　hardly　decomposes　below　200°C,　which　implies　that　the　working　performance　of　the　composite　PCM　is　relatively　stable　within　the　temperature　range　of　100°C.　Therefore,　the　composite　can　exhibit　excellent　thermal　stability　in　the　field　of　building　heating.　©　2022