An　experimental　investigation　was　conducted　to　investigate　the　axial　compressive　behavior　of　square　longitudinal-seam　steel　tubular　(LSST)　stub　columns　with　artificial　crack　defect　in　weld.　The　axial　compression　tests　were　carried　out　on　108　square　LSST　stub　columns　with　crack　defect　and　3　square　LSST　columns　without　crack　defect　as　control　groups.　The　effect　of　design　parameters　such　as　thickness　of　tube,　length　and　width　of　crack　defect,　location　of　crack　defect　on　axial　compressive　behavior　of　square　LSST　columns　were　analyzed.　Test　results　involved　failure　modes,　load-displacement　behavior,　ultimate　strength,　initial　stiffness,　and　ductility　coefficient　of　all　specimens　were　presented.　The　corresponding　FE　models　of　square　LSST　columns　with　crack　defect　are　established　and　validated　by　comparison　with　experimental　results.　Test　results　have　demonstrated　that　crack　defect　often　led　to　stress　concentration,　causing　significantly　higher　strain　intensity　at　the　position　of　crack　defect　compared　to　other　areas.　Square　LSST　columns　with　crack　defect　exhibited　a　26%　lower　ultimate　strength　at　T　=　2.5　mm.　The　ductility　coefficient　enhanced　with　the　decrease　of　length　and　width　of　crack　defect.　However,　the　location　of　crack　defect　had　limited　effect　on　axial　behavior　of　LSST　columns.　In　addition,　parametric　formulae　of　ultimate　strength　for　square　LSST　columns　with　crack　defect　are　proposed,　which　achieved　high　accuracy.　The　research　results　could　provide　evaluation　reference　in　design　and　construction　of　LSST　column.　©　2023