Effects　of　design　parameters　characterizing　bridge　flutter　sensitivity　on　flutter　critical　wiiul　speed　am　important　tools　fur　exploring　briilge　Duller　iitcchanism　aiul　improving　flutter　[lerformance.　Here,　In　assist　designers　in　efficiently　am!　accurately　obtaining　influence　laws　of　structural　dynamic　characteristics　and　flutter　derivatives　on　flu　Hit　performance　(if　large-span　bridge　during　design　phase,　a　bridge　3-D　flu　Hit　sensitivity　analysis　utclhml　based　on　＜lin;trt　ilifferetllial　inellmil　was　pnt[＜oseil.　This　melliml　was　liased　im　orthogonal　cliaracteristics　(if　left　and　right　eigenvectors　(if　a　system　matrix　to　construct　normalization　conditions　for　mulli-utodal　coupled　duller　of　bridge　under　small　perturbation　of　design　parauteters.　Combining　flutter　critical　conditions,　sensitivities　of　system　eigenvalues　and　flutter　eritieal　wiml　speed　to　＜k*sign　parauteters　were　obtained.　To　examine　the　proposed　method,　a　simply　supported　beam　bridge　with　ideal　thin　flat　plate　cross-seetion　was　taken　as　an　example,　the　results　obtained　with　the　proposed　melliml　was　eompared　with　thine　obtained　with　the　finite　difference　method,　it　was　shown　that　the　proposed　melliml　has　higlier　accuracy　and　computational　efficiency.　Tin-　prop(»-ed　melliml　was　applied　in　tin-　flutter　sensitivity　analysis　of　a　large-span　suspension　bridge.　The　results　showed　that　for　a　large-span　bridge　with　a　closed　streamlined　ginler　section,　tin-　flrsl-onlir　symmetric　vertical　bending　mole　and　tin*　first-order　symmetric　torsion　utoilc　have　tlte　largest　imparl　on　briilge　flutter;　increasing　damping　ratio,　modal　mass　and　foundation　torsion-bending　frequency　ratio　of　briilge　structure　can　all　increase　lite　critical　wind　speed　of　briilge　flutter;　in　flutter　derivatives.　1:＂　has　tin*　most　significant　impact　on　briilge　flutter　critical　wind　spired,　followed　by　.4,*　.　A＇　and　//,＂　.　while　tin-　others　can　basically　be　ignored.　©　2024　Chinese　Vibration　Engineering　Society.　All　rights　reserved.