Concrete-filled　double　skin　steel　tubes　(CFDST)　have　been　studied　by　several　researchers　in　the　past　few　years.　However,　these　members　when　subjected　to　sustained　loading　have　not　been　addressed　satisfactorily.　This　paper　carried　out　a　series　of　tests　on　CFDST　columns　with　circular　section　inner,　square　or　circular　section　outer　performed　under　long-term　sustained　loading　condition.　The　test　process　included　two　stages,　i.e.,　long-term　service　test　and　ultimate　strength　test.　The　long-term　deformation　of　the　CFDST　columns,　as　well　as　the　influence　of　long-term　sustained　loading　on　the　ultimate　strength　of　the　specimens,　was　investigated　experimentally.