Concrete-filled　steel　tubular　(CFST)　columns　are　widely　used　as　major　load-bearing　components　in　structures　due　to　their　excellent　load-bearing　properties.　However,　the　presence　of　steel　tube　makes　it　difficult　to　accurately　assess　the　damage　level　of　concrete　by　traditional　mechanical　measurements　alone.　This　paper　investigated　the　efficiency　of　acoustic　emission　(AE)　technique　in　assessing　the　damage　characteristics　of　the　concrete　in　CFST　columns.　The　damage　properties　of　four　axially　compressed　square　CFST　columns　with　the　widths　of　500-1000　mm　and　the　width-to-thickness　ratios　of　40　and　50　were　analyzed　through　AE　signals.　According　to　the　AE　results,　the　axial　compression　progress　of　specimens　could　be　divided　into　five　stages.　Then,　through　the　correlation　analysis,　the　cumulative　AE　energy,　amplitude,　and　hits　were　found　to　be　linear　related　to　the　applied　load.　Finally,　the　damage　percentage　of　each　specimen　at　different　stages　was　discovered　to　be　influenced　by　width　and　width-to-thickness　ratio.