An　experimental　study　on　six　axially-loaded　composite　short　columns　with　different　thicknesses　of　steel　tube　and　that　of　the　concrete　plate　was　carried　out.　Compared　to　the　mechanical　behavior　of　component　specimens　under　axially　compressed,　the　failure　modes,　compression　deformation,　and　strain　process　were　obtained.　The　two　main　parameters　that　have　a　significant　enhancement　to　cross-sectional　strength　were　also　analyzed.　The　failure　of　an　axially　loaded　UHPC-CFST　short　column　is　due　to　the　crushing　of　the　UHPC　plate,　while　the　CFST　member　does　reach　its　maximum　resistance.　A　reduction　coefficient　K　＇　c,　related　to　the　confinement　coefficient,　is　introduced　to　account　for　the　contribution　of　CFST　members　to　the　ultimate　load-carrying　capacity　of　the　UHPC-CFST　composite　short　columns.　Based　on　the　regression　analysis　of　the　relationship　between　the　confinement　index　xi　and　the　value　of　fcc/fc,　a　unified　formula　for　estimating　the　axial　compressive　strength　of　CFST　short　columns　was　proposed,　combined　with　the　experimental　results　in　this　research,　and　an　equation　for　reliably　predicting　the　strength　of　UHPC-CFST　composite　short　columns　under　axial　compression　were　also　proposed.