Multi-cell　concrete-filled　steel　tube　(MCFST)　columns　are　widely　used　in　super　high-rise　buildings.　However,　related　studies　on　their　axial　compression　behavior　are　limited.　In　order　to　propose　calculation　model　and　design　advice,　three　concrete-filled　steel　tube　column　samples　were　designed　and　constructed　for　testing.　The　samples　varied　in　their　cross-sections　(i.e.,　basic　type　with　reinforcement　cage,　simplified　type　without　reinforcement　cage,　and　reinforced　type　with　circular　steel　tube).　Damage　evolution,　load-bearing　capacity,　stiffness　degradation,　ductility,　and　restoration　capacity　were　analyzed　to　investigate　the　effect　of　different　sections.　Experimental　results　showed　that　the　reinforcement　cage　effectively　improved　the　bearing　capacity.　Due　to　the　excellent　mechanical　behavior　of　the　concrete-filled　circular　steel　tube,　the　comprehensive　behaviors　including　the　bearing　capacity,　ductility,　and　restoration　capacity　of　the　samples　improved.　The　confinement　mechanism　of　MCFST　was　analyzed　based　on　the　test　results.　A　＂separation　model＂　was　proposed,　followed　by　calculating　the　load-deformation　curves　of　12　samples　with　various　shapes　and　structures,　which　considered　that　the　MCFST　was　composed　of　several　single　cells,　and　calculating　the　constitutive　relationship　of　concrete　in　every　cell　individually.　Bearing　capacity　errors　were　approximately　+/-　5%,　and　errors　of　ultimate　deformation　were　approximately　+/-　15%,　showing　good　agreement　with　the　test　results.　This　data　indicates　that　the　constitutive　relationship　of　concrete　based　on　the　＂separation　model＂　is　reasonable.　Furthermore,　the　ultimate　state　of　every　individual　MCFST　cell　was　calculated　based　on　the　＂separation　model,＂　indicating　that　the　model　can　be　used　to　assist　in　MCFST　design.