The　conception　of　stress　wave　impedance　is　introduced　and　a　practicable　method　to　select　damping　parameter　in　structural　dynamic　analysis　is　presented,　in　which　the　impedance　and　damping　are　considered　to　be　numerically　equal　to　each　other　under　a　given　condition　in　calculation　of　the　initial　structural　damping　coefficient.　Theoretical　analysis　has　verified　the　consistency　of　viscous　damping　theory　and　complex　damping　theory　based　on　the　elastic　stress　wave　theory　for　both　rods　in　axial　vibration　and　beams　in　transverse　vibration.　This　approach　can　be　applied　to　determine　the　parameter　distribution　of　structural　damping　characteristics.　Taking　Jiangdou　Grade-separation　of　Fu-Quan　Expressway　as　an　example,　the　calculated　damping　ratio　of　simply　supported　plate　beams　for　the　first　mode　amounts　to　5.556%,　and　the　corresponding　damping　ratio　at　the　varying　observation　points　of　the　plate　beams　lies　between　5.02%　and　5.54%　by　means　of　half-power　method　in　an　ambient　random　vibration　test.　The　results　demonstrate　the　validity　of　the　developed　approach　to　engineering　practice.