The　spectral　element　method　(SEM)　is　extended　to　study　the　vibration　band-gap　characteristics　of　periodic　rigid　frame　structures　composed　of　Timoshenko　beams.　The　tensional　and　bending　elements　are　taken　into　account　for　deducing　the　element　stiffness　matrices　which　are　assembled　to　establish　the　spectral　equations　of　motion　of　the　whole　rigid　frame　structure.　The　validity　and　accuracy　of　the　natural　frequencies　and　frequency　responses　obtained　by　the　SEM　are　verified　by　comparing　the　present　numerical　results　with　the　results　of　the　experiments　and　the　finite　element　method　(FEM).　The　results　indicate　that　the　SEM　is　very　suitable　for　analyzing　the　dynamic　response　and　vibration　band-gap　properties　of　the　periodic　frame　structures,　and　the　SEM　is　more　effective　and　accurate　than　the　FEM,　especially　for　the　high　frequency　responses.　The　influences　of　the　structural　and　material　parameters　on　the　vibration　band-gaps　are　analyzed,　and　some　new　configurations　of　the　periodic　rigid　frame　structures　are　designed　to　obtain　more　and　wider　frequency　band-gaps　and　consequently　to　improve　the　structural　vibration　isolation　capability.