The　paper　presents　the　experimental　and　analytical　modal　analysis　of　a　steel-girder　arch　bridge.　The　field　test　is　carried　out　by　ambient　vibration　testing　under　traffic　and　wind-induced　excitations.　Both　the　peak　picking　method　in　the　frequency　domain　and　the　stochastic　subspace　identification　method　in　the　time　domain　are　used　for　the　output-only　modal　identification.　A　good　agreement　in　identified　frequencies　has　been　found　between　the　two　methods.　It　is　further　demonstrated　that　the　stochastic　subspace　identification　method　provides　better　mode　shapes.　The　three-dimensional　finite　element　models　are　constructed　and　an　analytical　modal　analysis　is　then　performed　to　generate　natural　frequencies　and　mode　shapes　in　the　three-orthogonal　directions.　The　finite　element　models　are　validated　to　match　the　field　natural　frequencies　and　mode　shapes.　It　is　observed　that　the　finite　element　Model-2　with　the　concrete　slab　provides　the　greater　stiffness　in　the　transverse　direction　of　the　bridge.　The　finite　element　Model-1　with　the　lumped　masses　agrees　well　with　the　field　tests　and　can　serve　as　a　baseline　model　of　the　bridge.