Three　mathematical　models　were　used　to　simulate　heat　transfer　of　a　phase　change　material　in　annular　channel.　The　models　used　are　the　pure　conduction　model　in　which　the　effect　of　natural　convection　is　ignored,　Boussinesq　model　and　the　equivalent　thermal　conductivity　model　in　which　natural　convection　is　considered.　Temperature　distribution　and　melting　interface　of　the　phase　change　material　in　annular　channel　have　been　studied　numerically.　The　results　indicate　that　the　impact　of　natural　convection　cannot　be　ignored,　otherwise　the　accuracy　of　heat　transfer　will　be　doubted.　Boussinesq　model　can　show　a　very　similar　temperature　distribution　and　melting　interface　to　the　experimental　results　or　to　the　actual.　But　it　is　too　complicated　for　application.　Although　the　equivalent　thermal　conductivity　model　could　not　show　a　temperature　distribution　and　melting　interface　consistent　with　the　actual,　it　is　the　most　appropriate　model　for　industry　to　calculate　the　energy　storage　and　heat　transfer　efficiency.