Finite　element　analysis　(FEA)　is　conducted　to　investigate　the　structural　behaviour　of　axially-loaded　ultra-high　strength　concrete　(UHSC)　filled　steel　tube　circular　columns　in　this　paper.　A　new　stress-strain　model　of　UHSC　confined　by　circular　steel　tube　is　proposed　by　recalibrating　the　existing　normal　strength　concrete　constitutive　model.　The　comparison　between　FEA　predictions　and　test　results　indicates　that　the　proposed　FEA　model　is　able　to　capture　the　brittleness　characteristic　of　UHSC　in　circular　CFST　columns　accurately.　Based　on　the　proposed　FEA　model,　the　structural　performance　of　axially-loaded　UHSC　filled　steel　tube　circular　columns,　including　load　versus　deformation　relationship,　stress　development,　confinement　effect　and　preliminary　optimized　design,　are　analysed　and　discussed.　Finally,　a　parametric　study　is　conducted　to　investigate　the　influence　of　key　parameters　on　the　load-deformation　curve　and　strength　utilization　index　of　axially-loaded　UHSC　filled　steel　tube　circular　column　during　the　entire　loading　process.