CFST　dumbbell-shaped　cross-section　is　widely　used　in　arch　ribs.　Though　its　flexural　stiffness　in　plane　is　strong,　it　is　weak　in　out-of-plane　and　it　has　a　weak　torsional　stiffness.　Therefore,　the　spatial　stability　is　a　key　issue　in　the　CFST　dumbbell　arch　bridge　at　present.　However,　that　is　shortage　of　research　in　this　aspect　at　present.　In　this　paper,　five　dumbbell-shaped　CFST　specimens　under　torsional　load　are　carried　out.　In　the　test,　the　distance　between　two　tubes　and　webs　are　selected　as　experimental　parameters.　Based　on　test　results,　curves　of　torsional　moment-angle　displacement,　torsional　mechanisms　and　failure　modes　of　the　specimens　are　analyzed.　It　is　shown　from　the　tests　that　the　torsional　rigidity　and　carrying　capacity　to　CFST　dumbbell-shaped　member　are　greater　than　those　of　single　tubular　member,　and　have　good　elastoplastic　and　ductile　property.　The　distance　of　two　web　plates　(width　of　web　space)　affects　the　torsional　stiffness　more　than　the　distance　between　two　tubes　(height　of　web　plate).　Finite　element　models　are　established　to　analyze　the　specimens.　The　analyzed　results　of　finite　element　method　consist　with　the　measured　results　very　well.　The　calculation　methods　of　nonlinear　torsional　stiffness　and　carrying　capacity　are　presented.