Although　there　are　many　literatures　about　effects　of　temperature　on　bridge　structures＇　frequencies　and　related　statistical　methods,　few　studies　reflect　dynamic　performance　and　time-varying　frequency　characteristics　of　bridge　structures　under　the　combined　action　of　multi-environmental　factors.　Adopting　the　co-integration　theory　with　the　ability　to　quantify　the　long　term　balance　relationship　among　multiple　non-stationary　sequences,　a　3-span　RC　bridge　model　under　natural　environment　were　monitored　and　analyzed　continuously,　a　model　for　long-term　balance　of　temperature-humidity-frequency　based　on　the　co-integration　theory　was　established　to　study　the　comprehensive　effects　of　temperature　and　humidity　on　the　bridge＇s　frequencies.　The　results　demonstrated　that　the　established　model　has　a　better　fitting　precision　and　a　predictive　ability,　it　can　fully　reflect　essential　characteristics　of　influences　of　temperature　and　humidity　on　bridge　frequencies;　based　on　this　co-integration　model,　the　bridge　frequency　modification　model　considering　effects　of　multi-environmental　factors　is　proposed　to　effectively　eliminate　effects　of　temperature　and　humidity　on　bridge　frequencies,　and　accurately　reveal　bridge＇s　dynamic　feature　variation　due　to　structures＇　internal　causes,　it　can　provide　effective　information　for　bridge　damage　diagnosis　and　safety　assessment.　©　2018,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.