A　simple　three-dimensional　heat　transfer　model　is　developed　to　consider　the　hindering　effect　of　cracks　on　heat　transfer.　The　3D　heat　transfer　model　can　also　be　applied　to　numerical　methods　such　as　the　combined　finite-discrete　element　method　(FDEM),　discrete　element　method　(DEM),　discontinuous　deformation　analysis　(DDA),　the　numerical　manifold　method　(NMM),　and　the　finite　element　method　(FEM)　to　construct　thermo-mechanical　coupling　models　that　allow　these　methods　to　solve　thermal　cracking　problems　and　dynamically　consider　the　hindering　effect　of　cracks　on　heat　transfer.　In　the　3D　heat　transfer　model,　the　continuous-discontinuous　medium　is　discretized　into　independent　tetrahedral　elements,　and　joint　elements　are　inserted　between　adjacent　tetrahedral　elements.　Heat　transfer　calculations　for　continuous-discontinuous　media　are　converted　to　heat　conduction　in　tetrahedral　elements　and　the　heat　exchange　between　the　adjacent　tetrahedral　elements　through　the　joint　element.　If　the　joint　element　between　adjacent　tetrahedral　elements　breaks　(ie,　a　crack　generates),　the　heat　exchange　coefficient　of　the　joint　element　is　reduced　to　account　for　the　hindering　effect　of　cracks　on　heat　conduction.　Then　the　model　and　the　FDEM　are　combined　to　build　a　thermo-mechanical　coupling　model　to　simulate　thermal　cracking.　The　thermally　induced　deformation,　stress,　and　cracking　are　investigated　by　the　thermo-mechanical　coupling　model,　and　the　numerical　results　are　compared　with　analytical　solutions　or　experimental　results.　The　3D　heat　transfer　model　and　thermo-mechanical　model　can　provide　a　powerful　tool　for　simulating　heat　transfer　and　thermal　cracking　in　a　continuous-discontinuous　medium.