In　order　to　analyze　the　fire　response　of　a　whole　structure　under　fire　using　the　method　of　scaled　fire　model,　a　similarity　relation　model　for　fire　response　of　steel　structures　under　fire　was　firstly　developed　in　this　paper　based　on　the　fire　similarity　and　heat　conduction　theory.　Then　1/4　and　1/8　scale　fire　test　models　and　test　specimens　of　steel　frame　structures　were　designed　according　to　the　relationships,　and　experimental　studies　were　performed.　Finally,　comparative　analysis　of　air　temperatures,　structure　temperatures,　structure　deformation　and　structure　failure　was　carried　out.　The　results　show　that　the　similarity　model　is　reasonable　and　accurate,　and　the　bearing　capacity　and　stability　also　meet　the　similarity　model.　The　similarity　model　can　be　simplified　by　assuming　the　temperature　similarity　ratio　of　1　or　assuming　the　same　similarity　ratio　of　fire　and　structural　time.　The　deformation　of　the　maintenance　structures　and　the　external　ventilation　conditions　should　be　strictly　controlled　in　the　scale　fire　tests,　so　as　to　ensure　the　similarity　of　the　structure　under　high　temperature　during　the　post-failure　stage.　©　2019,　Engineering　Mechanics　Press.　All　right　reserved.