Core　concrete　subjected　to　confinement　effect　from　steel　tube　is　the　main　advantage　of　concrete　filled　steel　tubular　(CFST)　column　under　compression.　However,　this　beneficial　composite　action　could　be　weakened　even　destroyed　by　debonding,　which　is　almost　unavoidable　as　a　common　phenomenon　in　CFST　structures　and　has　not　been　considered　satisfactorily　by　current　design　codes.　In　this　paper,　the　influence　of　debonding　on　circular　CFST　stub　columns　was　investigated　experimentally　and　numerically.　The　main　experimental　parameters　were　the　debonding　arc-length　ratio,　the　confinement　factor　and　the　load　mode.　Meanwhile,　the　finite　element　models　were　implemented　using　the　ABAQUS　finite　element　software,　of　which　the　validity　and　accuracy　were　verified　by　test　results.　Utilising　the　finite　element　model,　the　parametric　analysis　was　carried　out　to　study　the　influence　of　the　following　parameters　on　the　ultimate　load　capacity　of　debonding　specimens:　debonding　arc-length　ratio,　debonding　thickness　and　confinement　factor.　Based　on　the　results　of　parametric　analysis,　a　simplified　calculation　formula　was　proposed　to　calculate　the　ultimate　load　capacity　of　circular　CFST　stub　columns　with　debonding.　(C)　2011　Elsevier　Ltd.　All　rights　reserved.