The　effective　length　(or　calculating　length)　of　concrete　filled　steel　tubular　(CFST)　frame　columns　are　same　as　steel　frame　column　in　present　design　code,　but　they　have　different　mechanics　performance　and　model　of　instability　under　axial　loads.　On　the　base　of　nonlinear　elastic-plastic　FEM　analysis　theory　of　CFST　frames　with　CFST　columns　and　steel　beams,　the　method　how　to　calculate　the　effective　length　of　CFST　frame　columns　is　given.　Advanced　analysis　and　parameters　study　of　a　typical　portal　CFST　planar　frame　was　proceeded　by　the　FEM　method.　There　are　some　primary　discussions　about　the　effective　length　value　of　CFST　frame　columns　in　usual　engineering　practice.　Some　parameters,　such　as　physical　and　geometrical　values　of　the　columns　and　the　whole　frame,　were　considered　in　the　analysis.　So　some　recommendations　for　design　CFST　planar　frame　columns　are　given　at　the　end　of　the　paper.