Modal　identification　of　the　Shuikou　concrete　gravity　dam　has　been　conducted　based　on　natural　excitation　technique　and　Hilbert-Huang　transform　under　four　different　seismic　excitations　on　it.　A　new　approach　is　proposed　by　bandpass　filtering　technology　combining　with　the　modal　identification　method,　which　avoids　the　phenomenon　of　frequency　mixed　effectively　during　the　signal　decomposition,　thus　improving　the　accuracy　and　reliability　of　the　modal　parameter　identification.　Firstly,　a　simple　example　of　structural　dynamics　was　used　to　verify　the　correctness　of　the　method,　and　then　this　method　was　used　for　concrete　gravity　dam　modal　parameter　identification　for　the　first　time.　The　results　show　that　the　frequencies　identified　by　HHT+NExT　are　slightly　larger　than　the　result　of　the　peak-picking　method　and　ARX　model,　and　close　to　the　results　of　FEM.　Damping　ratios　identified　by　HHT+NExT　are　also　somewhat　larger　than　the　results　of　the　peak-picking　method　and　ARX　model,　and　meanwhile,　they　are　slightly　less　than　the　design　specification　ranges　namely　between　5%~10%　of　the　lower　limit　of　5%　in　specifications　for　seismic　design　of　hydraulic　structures.