Taking　a　RFB　(Rigid　Frame　Bridge)　as　engineering　background,　the　applicability　of　SIDM　(Seismic-isolation　Design　Method)　was　studied.　Two　different　SIDM　were　adopted,　which　were　GSDM　(Girder　Seismic-isolation　Design　Method)　and　BSDM　(Base　Seismic-isolation　Design　Method).　LVD　(Liquid　Viscous　Damper)　was　basic　component　of　GSDM,　and　RB　(Laminated　Rubber　Bearing)　was　basic　component　of　BSDM.　It　was　found:　GSDM　could　decrease　seismic　displacements　of　girder　and　seismic　forces　of　main　pier,　but　would　increase　seismic　forces　of　transition　pier.　BSDM　could　decrease　seismic　forces　of　main　pier,　but　would　increase　seismic　displacements　of　girder.　Compared　with　using　GSDM　or　BSDM　alone,　couse　of　them　would　not　only　inhibit　the　adverse　effects,　but　also　enhance　the　beneficial　effects.