A　damage　identification　method　based　on　axial　vibration　was　presented　on　the　basis　of　theoretical　derivation　axial　vibration　differential　equation　and　analytical　solution　of　three　kinds　of　support　form.　This　method　takes　the　second　derivative　of　low-level　axial　vibration　modal　shape　as　damage　index　without　the　dynamic　fingerprints　of　undamaged　structure.　The　index　is　very　sensitive　to　both　the　location　and　degree　of　structural　damage,　which　can　accurately　locate　and　calibrate　the　damage.　That　is,　it　will　change　to　the　opposite　direction　suddenly　in　the　damage　position.　Mutations　amplitude　increases　with　the　degree　of　damage.　Steel　components　are　experimented　and　tested,　the　results　also　proved　the　feasibility　and　viability　of　the　proposed　method.