Large-scale　structure　in　the　long-term　use　will　be　due　to　various　factors,　damage　and　degradation,　if　it　is　not　promptly　discovered　and　take　the　necessary　measures,　there　may　be　serious　accidents,　resulting　in　huge　loss　of　life　and　property.　Therefore,　it　is　very　important　to　evaluate　the　health　of　the　structure　in　a　timely　manner,　and　damage　identification　is　a　key　technology　in　structural　health　testing.　In　this　paper,　damage　is　identified　by　the　change　of　structural　dynamic　characteristics,　and　the　wavelet　transform　is　used　to　decompose　the　dynamic　response　signal　of　the　structure.　The　wavelet　packet　energy　spectrum　is　used　to　study　the　damage　detection　of　the　structure.　The　energy　spectrum　of　each　order　signal　is　obtained　by　decomposing　the　dynamic　response　signal　by　wavelet　analysis　in　MATLAB　simulation　software,　and　the　change　of　energy　spectrum　before　and　after　structure　damage　is　obtained　for　the　online　damage　detection　of　the　structure.　In　this　paper,　the　damage　of　a　large　span　bridge　structure　is　analyzed　and　the　necessary　measures　for　earthquake　disaster　reduction　are　put　forward.　The　results　show　that　the　structural　damage　detection　which　is　based　on　wavelet　analysis　is　feasible,　so　that　the　disaster　prevention　and　mitigation　work　is　carried　out.