This　paper　reports　the　compressive　behavior　of　concrete-filled　double　skin　steel　tubular　(CFDST)　columns　strengthened　by　CFRP　under　axial　loading.　The　outer　skin　was　made　of　square　hollow　sections　(SHS),　while　the　inner　skin　was　made　of　circular　hollow　sections　(CHS).　Twelve　CFDST　columns　strengthened　by　CFRP　and　three　CFDST　columns　were　tested.　The　failure　mode,　load-displacement　relationship,　axial　load-carrying　capacity　and　initial　stiffness　are　given　and　analyzed.　The　results　showed　that　the　CFDST　columns　strengthened　by　CFRP　have　better　mechanical　properties　than　the　column　without　CFRP　reinforcement　(i.e.　the　CFDST　columns).　The　CFDST　columns　strengthened　by　CFRP　eventually　failed　due　to　CFRP　rupture　or　buckling　of　the　external　steel　tube　near　the　end　and　cracked　concrete　damage　from　the　outer　steel　tube.　The　stiffness　and　axial　load　bearing　capacity　of　the　column　can　be　improved　as　the　number　of　CFRP　layers　increases.　A　simplified　design　formula　of　CFDST　columns　strengthened　by　CFRP　is　proposed,　which　is　in　good　agreement　with　the　experimental　results.