The　concrete-filled　double-tube　(CFDT)　columns　have　been　proposed　in　recent　years.　The　existence　of　inner　steel　tube　can　not　only　increase　the　confinement　on　core　concrete,　but　also　increase　its　fire　resistance　and　anticorrosion　performance.　This　makes　it　have　a　great　application　prospect　in　the　field　of　ocean　structure　engineering.　In　this　paper,　the　axial　compression　performance　of　square　CFDT　short　columns　is　comprehensively　analyzed.　The　specimens　studied　consist　of　an　external　steel　tube　(square　hollow　section)　and　an　inner　steel　tube　(circular　hollow　section),　in　which　concrete　is　completely　filled.　The　fine　finite　element　(FE)　method　is　used　to　simulate　the　performance　of　this　column.　Two　constitutive　models　of　confined　concrete　for　square　CFDT　core　concrete　are　proposed.　In　order　to　ensure　the　correctness　of　the　model,　the　verification　analysis　of　the　model　is　carried　out　based　on　the　previous　experimental　results,　and　the　whole　process　of　axial　compression　performance　of　CFDT　columns　is　analyzed　in　detail.　The　concrete　strength　(f(c)＇),　width-thickness　ratio　(B/t(o)),　diameter-thickness　ratio　(d/t(i)),　diameter-width　ratio　(d/B)　and　yield　strength　(f(y))　of　square　CFDT　columns　are　compared　and　analyzed.　The　performance　of　CFDT　columns　with　the　same　steel　content　is　also　analyzed,　it　is　of　great　significance　to　improve　the　application　of　CFDT　columns　in　marine　environment　or　high　temperature　environment.　Finally,　new　formulas　for　calculating　the　ultimate　bearing　capacity　of　CFDT　short　columns　under　axial　compression　are　proposed.　The　results　show　that　the　new　formulas　can　predict　the　strength　of　CFDT　short　columns　well.