The　experiment　of　restrained　CFST　(concrete　filled　steel　tube)　dumbbell　shaped　members　under　torsion　loads　was　carried　out　and　the　finite　element　model　was　established.　The　calculation　formula　of　torsional　bearing　capacity　of　CFST　dumbbell　shaped　cross　section　was　derived.　The　results　show　that　CFST　dumbbell　shaped　members　show　good　torsional　elastic-plastic　property.　Increasing　the　width　of　web　interspace　can　remarkably　improve　the　torsional　property　for　dumbbell　shaped　members,　while　the　effects　of　changing　height　of　web　interspace　can　be　negligible.　The　torsional　bearing　capacity　of　the　CFST　dumbbell　shaped　members　can　be　considered　as　the　sum　of　steel　members　(the　upper　and　lower　steel　tubes　and　the　steel　webs),　the　concrete　filled　in　the　tubes　and　the　concrete　filled　in　the　web　interspace.　The　proportion　of　the　concrete　filled　in　the　web　interspace　for　torsional　bearing　capacity　is　less　than　5%　and　thus　its　effects　can　be　negligible.　The　derived　and　simplified　formula　can　be　used　to　calculate　the　torsional　bearing　capacity　of　the　CFST　dumbbell　shaped　members　with　more　simplicity　and　accuracy.