This　paper　presents　a　novel　shape-stable　phase　change　material　(PCM)　composite　for　thermal　energy　storage　applications.　The　formulation　of　the　material　consists　of　the　components:　eutectic　nitrate　(NaNO3-KNO3)　as　thermal　storage　material,　expanded　graphite　(EG)　for　improving　structural　stability　and　thermal　conductivity,　and　SiO2　nanoparticles　for　improving　specific　heat.　The　material　was　successfully　prepared　by　the　mechanical　dispersion　method.　The　effects　of　EG　and　SiO2　nanoparticles　additives　on　the　thermophysical　properties　of　the　composite　were　investigated　by　SEM,　STA,　and　LFA.　The　results　showed　that　EG,　SiO2　nanoparticles　and　eutectic　nitrate　have　excellent　chemical　compatibility.　The　specific　heat　of　the　composite　was　3.92　J/(g.K),　which　was　2.58　times　higher　than　that　of　eutectic　nitrate　when　the　content　of　EG　and　SiO2　nanoparticles　was　15　wt%　and　1　wt%,　respectively.　The　latent　heat　of　the　composite　decreased　with　the　increase　of　EG　mass　fraction,　but　overall　an　increase　in　energy　storage　density　was　found　due　to　the　addition　of　SiO2　nanoparticles.　The　thermal　conductivity　of　the　composite　with　15　wt%　EG　and　1　wt%　SiO2　nanoparticles　was　significantly　increased　by　about　16.2　times　compared　with　that　of　eutectic　nitrate.　Furthermore,　thermal　cycle　stability　was　tested.　The　NaNO3　KNO3/1　wt%　nano-SiO2/15　wt%　EG　composite　showed　no　obvious　specific　heat　change　after　100　thermal　cycles　and　100　h　high-temperature　test,　respectively.　The　prepared　NaNO3-KNO3/nano-SiO2/EG　composite　has　a　promising　application　prospect　in　the　high-temperature　energy　storage.