The　wavelet　transform　is　used　as　the　time-frequency　representation　of　operational　measurement　signals　for　the　purpose　of　modal　parameter　identification　of　bridges.　In　this　paper,　the　use　of　a　new　identification　procedure,named　wavelet-based　identification　technique　of　bridges　modal　parameters　is　discussed.　The　technique　starts　with　the　calculation　of　covariance　from　random　response　of　the　system　that　converted　into　the　time-scale　domain　using　a　continuous　Morlet　wavelet　transform.　It　can　be　shown　that　the　ridges　of　the　covariance　wavelet　coefficient　magnitudes　contain　modal　information　of　the　system.　The　phase　angles　and　the　magnitudes　of　the　covariance　wavelet　coefficients　along　the　ridges　are　related　to　natural　frequencies　and　viscous　damping　ratios.　And　the　wavelet　coefficients　of　the　cross-covarianee　were　used　to　estimate　the　mode　shapes　of　the　system.　The　case　study　is　the　Beichuan　River　Bridge,　a　concrete　filled　steel　tubular　arch　bridge　in　Xining,　China　that　was　tested　under　ambient　vibration　excitation.　The　modal　parameters　such　natural　frequencies,　damping　ratios　and　mode　shapes　are　successfully　identified　by　proposed　wavelet-based　technique.　The　obtained　results　have　been　comparable　with　those　previously　obtained　from　the　peak　pick　method　in　frequency　domain　and　stochastic　subspace　identification　in　time　domain.　It　is　demonstrated　that　the　wavelet　transform　is　promising　in　the　modal　parameter　identification　of　structures　under　operational　measurements.