To　improve　the　seismic　performance　of　circular　concrete-filled　steel　tube　(CFST)　columns　with　large　dimensions,　circumferential　stiffeners,　vertical　stiffeners,　and　reinforcement　cages　were　suggested　to　be　set　in　the　columns.　Seven　circular　CFST　column　specimens　with　four　internal　constructions　and　two　shear-span　ratios　were　designed　and　tested　under　low-frequency　cyclic　loading.　The　failure　modes,　hysteretic　behavior,　bearing　capacity,　ductility,　stiffness　and　strength　degradation,　energy　dissipation　capacity,　and　effect　on　the　seismic　performance　based　on　different　internal　constructions　and　different　shear-span　ratios　were　herein　discussed　and　clarified.　The　test　results　illustrated　that　the　internal　constructions　could　effectively　postpone　the　local　buckling　of　steel　tube　and　improve　the　ultimate　strength,　ductility,　and　stiffness　of　circular　CFST　columns.　A　finite　element　(FE)　model　was　developed　to　carry　out　the　working　mechanism　and　parametric　analysis.　Finally,　a　theoretical　model　to　estimate　the　ultimate　bearing　capacity　of　CFST　columns　with　different　internal　constructions　was　established,　the　results　obtained　from　the　model　were　in　good　agreement　with　the　test　results.