The　behaviour　of　square　concrete　filled　stainless　steel　tubular　(CFSST)　stub　columns　after　exposure　to　elevated　temperatures　under　axial　compression　is　presented　in　this　paper.　A　total　of　sixty-nine　specimens　were　tested,　including　forty-eight　square　CFSST　stub　columns　at　elevated　temperatures　cooled　in　air,　nine　square　CFSST　stub　columns　at　elevated　temperatures　cooled　in　water　and　twelve　square　CFSST　stub　columns　left　untreated　at　ambient　temperature.　A　total　of　twelve　square　CFSST　stub　columns　were　carried　out　load-strain　tests.　The　main　parameters　explored　in　the　test　include　thickness　(1.0　mm,　1.2　mm,　1.5　mm,　2.0　mm),　concrete　strength　(C20,　C30,　C40),　temperatures　ranging　from　400　degrees　C　to　1000　degrees　C　and　cooling　methods.　This　paper　presents　the　failure　modes,　ultimate　load-bearing　capacity,　load-strain　curves,　load　versus　displacement　curves,　initial　compressive　stiffness　at　the　elastic　stage　and　ductility　of　the　specimens.　It　was　found　that　high　temperature　had　the　greatest　influence　on　the　ultimate　load-bearing　capacity　of　the　columns,　and　the　cooling　methods　also　had　some　effect　on　it.　As　the　elevated　temperature　to　which　the　specimens　were　subjected　increased,　the　percentage　of　the　ultimate　load-bearing　capacity　decrease　had　an　obvious　increase　and　the　ductility　of　the　specimens　was　enhanced.　The　initial　compressive　stiffness　decreased　evidently　as　the　temperature　increased　to　800　degrees　C.　A　new　failure　mode　was　identified　without　visible　corner　crack　in　the　specimens　after　exposure　to　elevated　temperatures　compared　with　the　specimens　at　ambient　temperature.　The　ultimate　load-bearing　capacity　increased　and　the　axial　deformation　versus　load　curves　had　a　longer　elastic　stage　as　the　concrete　strength　increased.