This　study　mainly　presented　a　pseudo-static　experiment　on　two　full-scale　square　CFST　short　columns　with　the　cross-sectional　width　of　600　mm　under　combined　constant　axial　load　and　cyclic　lateral　load.　The　seismic　performance　of　the　two　full-scale　CFST　columns　were　investigated.　Meanwhile,　the　plastic　hinge　length　of　the　specimens　was　discussed.　The　test　results　presented　that　the　specimens　suffered　bend-shear　failure.　The　local　buckling　of　steel　tube　occurred　at　the　end　of　the　specimens　and　the　core　concrete　crushed.　The　safety　redundancy　of　lateral　bearing　capacity　decreased　in　full-scale　specimen.　By　the　method　of　physical　observation,　the　plastic　hinge　length　Lp1　was　determined　mainly　according　to　the　range　of　the　local　buckling　of　steel　tube.　There　had　a　great　difference　between　the　prediction　of　plastic　hinge　lengths　by　the　existing　calculation　model　and　the　plastic　hinge　lengths　obtained　by　the　test.　©　The　Authors,　published　by　EDP　Sciences,　2021.