Based　on　the　ambient　vibration　testing,　effects　of　environmental　temperature　on　the　vibration　characteristics　of　a　rigid　frame　arch　bridge　and　a　two-span　continuous　composite　beam　were　conducted.　The　testing　results　indicate　that　the　changes　of　environmental　temperature　cause　great　variation　of　bridge　vibration　characteristics.　It　can　also　be　found　that　the　restrictions　of　boundary　condition　may　affect　bridge　dynamic　characteristics　extensively　when　the　environmental　temperature　changes.　The　testing　and　anlysis　can　be　used　for　bridge　health　monitoring　and　structural　damage　identification.