To　multi-tower　suspension　bridge,　reasonable　design　of　middle　tower　is　very　important.　In　this　paper,　a　three-tower　self-anchored　suspension　bridge　(TSSB)　was　taken　as　research　background.　The　effect　of　middle　tower　stiffness　and　mass　on　static　and　dynamic　performance　of　TSSB　was　discussed.　Through　dynamic　characteristic　analysis,　we　got　the　modes　whose　nature　frequencies　were　affected　obviously　by　middle　tower　stiffness.　The　seismic　parameter　analysis　showed　that　rigid　and　light　weight　middle　tower　was　benefit　to　seismic　performance　of　TSSB.　At　last,　this　paper　concludes　that　designer　should　consider　static　and　dynamic　performance　of　TSSB　comprehensively　in　the　design　of　middle　tower.