In　order　to　calculate　vertical　vibration　frequencies　of　multi-tower　self-anchored　suspension　bridge　(MSSB)　conveniently,　the　three-tower　self-anchored　suspension　bridge　(TSSB)　was　taken　as　research　object,　which　is　the　simplest　type　of　MSSB.　Based　on　the　Rayleigh　method,　frequency　formulas　for　1st　anti-symmetric　and　symmetric　vertical　vibration　modes　of　TSSB　were　derived　in　consideration　of　the　influence　of　tower　stiffness　on　vibration　frequencies.　The　modal　test　results　of　scaled　TSSB　and　numerical　analysis　result　of　TSSB　were　taken　as　examples　to　check　the　accuracy　of　proposed　formulas　respectively.　The　results　show　that:　vertical　frequencies　are　significantly　affected　by　tower　stiffness　of　TSSB　and　the　extent　of　influence　can　be　assessed　by　the　main　tower　stiffness　coefficients　formulas.　The　errors　between　formulas　calculation　result　and　modal　test　result　or　numerical　analysis　result　are　within　3%,　which　shows　the　good　accuracy　of　the　frequency　formulas.