Experiments　of　10　concrete-filled-steel　tubular　(CFST)　dumbbell-shaped　Long　columns　with　various　slenderness　ratio　subjected　to　axial　load　were　carried　out,　in　which　5　specimen　were　failed　in　the　strong-stress-axis　direction;　another　5　were　failed　in　the　weak-stress-axis　direction.　It　is　proved　by　the　test　that　the　failure　of　dumbbell　shaped　specimen　in　strong-stress-axis　direction　can　be　realized　by　welding　corrugated　steel　webs　in　its　weak-stress-axis　direction　to　increase　flexible　rigidity　in　this　direction.　Similar　with　the　long　columns　of　single　tube　section,　the　load-carrying　capacity　and　the　elastic-plastic　tangential　stiffness　of　CFST　dumbbell-shaped　long　columns　decrease　with　the　increasing　of　slenderness　ratio.　But　elastic-plastic　instability　occurred　on　dumbbell-shaped　long　columns　instead　of　the　elastic　instability　in　one　of　single　tube　section　with　same　slenderness　ratio.　A　nonlinear　finite　element　method　is　provided　for　dumbbell-shaped　long　column,　and　the　influence　of　slenderness　ratio　on　its　load-carrying　capacity　is　analyzed　by　parametric　studies.　It　is　shown　that　the　stability　coefficient　of　dumbbell-shaped　long　CFST　columns　is　different　from　that　of　long　CFST　columns　of　single　tube　section.　However,　the　rules　of　load-carrying　capacity　in　the　weak-stress-axis　and　strong-stress-axis　directions　for　dumbbell-shaped　long　CFST　column,　varying　with　the　slenderness　ratio,　are　similar.　A　simplified　formula　to　calculate　the　stability　coefficient　is　presented　by　unifying　the　rule　in　two　directions.