During　the　service　of　structures,　local　damage　at　their　key　positions　will　continually　accumulate,　and　finally　lead　to　sudden　increase　of　structure　damage.　This　will　result　in　outburst　decrease　of　local　stiffness　and　reduction　of　structure　trait.　Traditional　modal　properties　are　poor　indications　of　damage.　In　this　study,　a　damage　detection　index,　namely,　wavelet　packet　energy　rate　index,　is　proposed　for　the　damage　detection　of　structures.　Dynamic　signals　measured　from　experiment　beams　are　first　decomposed　into　wavelet　packet　components,　then　wavelet　energy　rate　index　is　computed　and　used　to　detect　location　of　damage.　The　three　kinds　of　damage　locations　of　beams　in　laboratory　are　designed　to　prove　the　validity　of　energy　index　in　experiment.　The　results　show　that　the　WPT-based　energy　rate　index　is　good　candidate　index　that　is　sensitive　to　structural　damage.