Owing　to　their　exceptional　durability,　reinforced　sea-sand　concrete-filled　(square)　stainless　steel　tubular　(RSCFSST)　columns　present　a　viable　structural　solution　for　coastal　regions.　Axial　compressive　tests　were　conducted　on　eight　square　RSCFSST　short　columns　and　two　sea-sand　concrete-filled　(square)　stainless　steel　tubular　counterparts.　The　experimental　results　demonstrated　that　the　incorporation　of　stainless　steel　rebars　increased　their　axial　compressive　resistance,　peak　strain,　and　ductility　by　4–13　%,　21–52　%,　and　25–122　%,　respectively.　Notably,　RSCFSST　column　filled　with　sea-sand　concrete　exhibited　comparable　axial　compressive　behavior　to　those　columns　utilizing　normal　concrete.　A　finite　element　model　was　developed　to　conduct　the　mechanism　and　parametric　analyses.　The　mechanism　analysis　revealed　that　stainless　steel　outperformed　carbon　steel　in　improving　both　the　peak　strain　and　ductility　of　the　composite　columns.　Parametric　analysis　indicated　that　increasing　the　concrete　strength,　0.2　%　proof　strength　of　the　steel　tube,　0.2　%　proof　strength　of　stirrups,　steel　tubular　ratio,　or　stirrup　ratio　significantly　enhanced　the　axial　compressive　resistance　of　the　RSCFSST　columns.　Finally,　novel　predictive　methods　were　developed　for　estimating　their　axial　compressive　resistances　and　peak　strains,　demonstrating　superior　accuracy　in　predictions.　©　2025　The　Authors