Concrete-filled　thin-walled　double-tubular　(CFTDT)　columns　with　longitudinal　stiffeners　have　high　fire　resistance　and　economy.　Meanwhile,　the　concrete-filled　steel　tubular　members　are　widely　used　in　earthquake　prone　areas.　Thus,　it　is　necessary　to　study　its　seismic　performance.　Hysteretic　tests　of　six　CFTDT　columns　with　longitudinal　stiffeners　were　conducted.　Main　parameters　include　the　axial　compression　ratio　and　the　outer　diameter　of　outer　steel　tube.　The　test　results　show　that　the　hysteretic　loops　of　the　composite　columns　are　stable　and　the　seismic　behaviors　are　good,　meanwhile　the　bearing　capacity　and　energy　dissipation　capacity　of　the　composite　columns　are　significantly　higher　than　those　of　the　concrete-filled　cold-formed　thin-walled　steel　tubular　counterpart　with　longitudinal　stiffeners;　The　failure　mode　of　the　specimens　is　combined　compressive　and　in-plane　bending　failure;　as　the　axial　compression　ratio　of　the　specimen　increases,　the　ductility　and　energy　dissipation　capacity　decrease,　and　the　rate　of　stiffness　degradation　also　accelerates　significantly;　as　the　outer　diameter　of　outer　steel　tube　of　the　specimen　increases,　the　strength,　ductility　and　energy　dissipation　capacity　increase.　However,　the　outer　diameter　of　outer　steel　tube　has　slight　effect　on　the　stiffness　degradation.　The　nonlinear　finite　element　(FE)　model　of　the　CFTDT　columns　was　developed　and　verified　by　test　results.　Based　on　this　FE　model,　the　parametric　analysis　was　conducted.　The　parameters　including　the　yield　strength　of　steel　tubes,　the　outer　concrete　strength,　the　axial　load　ratio,　the　diameter　to　width　ratio,　the　diameter　to　thickness　ratio　and　the　slenderness　ratio　have　significant　influences　on　the　bearing　capacity　of　the　composite　columns.　Based　on　the　parametric　analysis,　the　load-deflection　restoring　force　model　was　finally　proposed　for　composite　columns.　©　2020,　Editorial　Office　of　Journal　of　Building　Structures.　All　right　reserved.