In　this　paper,　a　new　modal　analysis　and　damage　identification　method　is　developed　for　bridge　structures,　in　which　the　vibration　modal　and　curvature　modal　can　be　obtained　by　natural　frequency,　and　so　local　damage　is　characterized　by　only　the　natural　frequency　measured　from　the　damaged　structures.　In　contrast　with　most　of　the　existing　vibration-based　damage　identification　methods,　which　require　both　the　natural　frequency　and　other　modal　parameters　measured　from　the　damaged　structure.　Finally,　a　computer　simulated　case　is　studied　on　a　beam　pined　at　edges　to　illustrate　capability　of　the　modal　data　and　the　damage　evaluating　method.