The　mode　perturbation　method　was　modified　and　the　improved　perturbation　method　(IPM)　was　used　to　solve　the　vibration　problem　of　non-uniform　beam　with　complete　elastic　supports　based　on　Bernoulli-Euler　beam　theory.　In　the　modal　subspace　of　an　equivalent　uniform　beam　with　complete　elastic　supports,　the　variable　coefficient　differential　vibration　equation　of　the　non-uniform　simply　supported　continuous　beam　with　complete　elastic　supports　was　converted　to　nonlinear　algebraic　equations.　The　semi-analytical　solution　of　dynamic　characteristics　of　non-uniform　beam　with　complete　elastic　supports　was　obtained　and　the　formula　of　coefficient　Δkki　was　given.　An　example　analysis　indicates　that　the　improved　perturbation　method　not　only　has　high　precision　and　good　convergency　but　also　considers　the　elastic　supports　effect　on　dynamic　characteristics.　A　simplified　calculating　method　(SIPM)　for　symmetrical　beam　was　proposed　based　on　the　symmetry　of　mode　shapes.　The　bearing　damage　effects　on　dynamic　characteristics　of　non-uniform　simply　supported　beam　bridge　were　discussed.　©,　2015,　Chinese　Vibration　Engineering　Society.　All　right　reserved.