The　variation　of　the　temperature　and　humidity　significantly　affects　the　modal　parameters　of　the　structure,　and　the　effect　and　the　quantitative　statistics　of　single　environmental　factors　such　as　temperature　on　the　frequency　of　bridge　are　intensively　studied,　but　the　study　on　the　mechanism　and　the　effective　model　considering　the　comprehensive　effect　of　multi-environmental　factors　is　relatively　rare.　The　principle　and　analysis　method　of　co-integration　is　introduced,　and　the　frequency-modified　method　based　on　co-integration　is　presented.　Through　the　monitoring　of　a　three-span　concrete　bridge　model　in　the　natural　environment,　the　effective　monitoring　data　are　analyzed　to　establish　a　long-term　equilibrium　model　about　＂frequency-temperature-humidity＂　based　on　co-integration　theory.　The　experimental　results　indicate　that　the　model　has　a　better　fitting　ability　and　accuracy,　and　it　is　can　be　used　to　predict　the　variation　trend　of　frequency.　Based　on　the　mathematical　model　of　co-integration　analysis,　the　modified　frequency　model　considering　multi-environmental　factors　is　proposed,　which　can　eliminate　the　comprehensive　effect　of　temperature　and　humidity　on　frequency,　and　the　variation　of　dynamic　characteristics　due　to　the　internal　causes　of　structure　is　revealed.　The　extracted　sequence　can　provide　effective　information　for　further　safety　assessment　and　damage　detection　of　bridge.