With　the　development　of　radiant　floor　system　engineering　applications　in　civil　and　agricultural　buildings,　an　engineering　problem　has　been　gradually　becoming　urgent,　that　is　how　to　match　the　terminal　of　a　radiant　floor　system　for　changeable　and　flexible　application.　This　problem　is　closely　related　to　thermal　performance　of　the　floor.　Therefore,　it　is　very　important　and　necessary　to　study　the　heat　transfer　process　of　the　floor,　and　obtain　the　regulation　and　characteristics　of　heat　transfer　to　solve　it.　As　the　core　component　of　heat　transfer　in　radiant　floor　system,　the　floor　can　be　regarded　as　one　kind　of　special　heat　exchanger.　Based　on　the　basic　theory　and　parameters　of　heat　exchanger,　thermal　performance　can　be　analyzed　and　evaluated.　Based　on　the　application　of　thermal　resistance　in　series,　the　heat　transfer　of　multi-layer　floor　structure　is　equivalent　to　that　of　homogeneous　structure,　whose　analytical　solution　and　heat　resistance　of　floor　are　obtained.　Assuming　that　the　heat　conduction　in　pipes　wall　is　one-dimensional　problem,　the　thermal　resistance　of　the　wall　is　amended　after　the　model　based　on　the　equivalent　thermal　resistance.　Furtherly,　combined　with　the　basic　theory　of　the　thermal　design　of　the　heat　exchanger,　the　heat　transfer　effectiveness　Ε　is　raised　when　the　radiant　floor　is　regarded　as　some　kind　of　heat　exchanger.　According　to　the　heat　transfer　effectiveness,　the　number　of　transfer　units　can　be　obtained,　and　then　the　Ε-NTU　(number　of　transfer　units)　method　for　thermal　design　of　floor　structure　is　creatively　proposed,　which　is　compared　with　the　design　graph　and　design　tables　in　ASHRAE　(American　Society　of　Heating,　Refrigerating,　and　Air-Conditioning　Engineers)　Handbook.　Finally,　the　Ε-NTU　method　for　thermal　design　of　floor　structure　was　put　into　practice　for　the　designs　of　radiant　floor　system　in　the　buildings　located　in　Beijing.　According　to　the　supply　temperature　provided　and　the　heating　load　calculated,　the　total　thermal　resistance　of　floor　structure　was　obtained,　and　then　the　parameters　of　floor　layers　and　pipe　spacing　were　determined.　The　experimental　data　indicate　that　the　temperatures　of　the　rooms　meet　the　design　requirements　very　well.　It　shows　that　the　Ε-NTU　design　method　can　be　more　convenient　for　the　design　of　floor　heat　transfer　structure　with　flexible　application.　The　corresponding　floor　structure　can　be　determined　according　to　the　supply　temperature,　indoor　temperature　and　heating　load,　and　the　supply　temperature　can　be　determined　according　to　the　different　floor　structures.　The　floor　surface　temperature　under　the　supply　temperature　and　the　floor　structure　can　be　checked.　A　new　way　of　thinking　for　the　floor　thermal　design　is　provided.　©　2016,　Editorial　Department　of　the　Transactions　of　the　Chinese　Society　of　Agricultural　Engineering.　All　right　reserved.