Due　to　the　lack　of　adequate　research　and　deep　understanding　of　high-strength　concrete-filled　steel　tube　(CFST)　long　columns,　the　current　specifications　cannot　provide　the　available　guidelines　and　design　equations.　To　address　the　gap,　this　paper　investigates　the　axial　behavior　of　high-strength　rectangular　CFST　long　columns　by　experimental　database,　finite　element　analysis,　and　theoretical　modeling.　Firstly,　the　experimental　database　including　74　specimens　for　high-strength　rectangular　CFST　long　columns　was　compiled.　Then,　the　detailed　3D　non-linear　finite　element　method　(FEM)　models　were　developed　and　verified　for　parametric　studies.　The　effects　of　steel　yield　stress,　concrete　strength,　section　slenderness　ratio　and　slenderness　ratio　on　the　ultimate　strength　and　slenderness　reduction　factor　were　investigated.　Finally,　the　possibility　of　extending　the　current　design　equations　in　different　specifications　was　evaluated.　©　2023,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.