In　this　study,　tests　of　twenty-four　square　concrete　filled　steel　tubular　(SCFST)　columns　with　different　structural　sizes　by　the　pseudo-static　method　were　conducted　to　investigate　the　influence　of　the　confinement　effects.　In　addition,　the　structural　size　and　the　confinement　effect　are　respectively　represented　by　column　width　and　width-to-thickness　ratio.　The　experimental　results,　including　the　failure　mode,　the　lateral　load-displacement　curves　and　the　indices　of　the　seismic　performance　were　recorded　and　analyzed.　The　mode　of　failure　is　typical　compressive　flexure　pattern.　As　the　structural　size　increases　or　the　confinement　effect　decreases,　the　nominal　flexure　strength　of　SCFST　column　decreases.　Compared　of　the　nominal　flexural　strength　of　small　column,　the　influence　of　confinement　effect　is　more　significant　on　that　of　large　column.　The　displacement　ductility　coefficient,　the　mean　energy　dissipation　factor　and　the　relative　stiffness　decrease　with　the　increasing　column　width.　Then　enhanced　confinement　effect　has　no　obvious　influence　on　the　displacement　ductility　coefficient　of　the　SCFST　column.　When　the　confinement　effect　increases,　the　energy　dissipation　capacity　of　the　SCFST　column　increases.　Finally,　the　modified　calculated　method　considering　size　effect　is　established,　and　this　method　is　applicable　to　predict　the　bending　moment　of　the　SCFST　column　with　different　confinement　effects　and　structural　sizes.　©　2024　Elsevier　Ltd