A　finite-element　model　for　CFST　members　using　a　3D　composite　beam　fiber　element　is　presented　which　accounts　for　the　nonlinear　constitutive　models　of　steel　and　concrete　separately.　The　model　is　proved　to　be　valid　by　comparing　the　computational　results　of　some　test　specimens　with　their　experimental　data.　Using　this　model,　a　CFST　arch　bridge＇s　seismic　response　was　calculated.　The　result　indicated　that　the　magnitude　of　displacements　and　moments　at　arch　crown　increases　up　to　10　percent　caused　by　CFST　hysteretic　behavior　which　should　be　seriously　considered　during　seismic　design.　Some　measures　and　suggestions　bring　forward　to　guide　the　design　and　construction　of　this　type　of　bridge.　©　(2011)　Trans　Tech　Publications,　Switzerland.