This　paper　presents　a　study　on　the　mechanical　performance　of　the　square　concrete-filled　steel　tube　(CFST)　columns　under　the　axial　compression,　which　is　based　on　forty-eight　short　square　CFST　columns　subjected　to　lateral　impact.　The　concrete　compressive　strength,　impact　energy　and　impact　location　are　set　as　the　parameters　in　the　test.　This　paper　mainly　analyzes　the　effect　of　these　three　parameters　on　the　residual　ultimate　bearing　capacity　of　the　test　specimens.　The　result　indicates　that　the　lateral　impact　has　negative　influence　on　the　residual　ultimate　bearing　capacity,　initial　stiffness　and　ductility　of　the　CFST　columns.　The　impact　location　has　a　significant　influence　on　the　residual　ultimate　bearing　capacity.　The　residual　ultimate　bearing　capacity　decreases　as　the　impact　location　varies　from　the　middle-length　to　the　end　of　the　specimens.　The　test　result　indicates　that　the　lateral　impact　causes　an　evident　decrease　of　the　ductility　and　initial　stiffness　of　CFST　columns.　Ductility　increases　as　the　impact　location　varies　from　the　middle-length　to　the　end　of　the　specimens.　Besides,　the　strain　development　of　twelve　square　CFST　columns　during　the　experiment　is　investigated　in　this　paper.　Based　on　the　experimental　results,　a　calculation　formula　is　proposed　to　predict　the　residual　ultimate　bearing　capacity　for　the　specimens　tested,　and　a　good　agreement　with　the　experimental　results　is　achieved.　©　2017　Elsevier　Ltd