Modal　characteristics　analysis　is　the　basis　of　the　structural　dynamic　characteristics　analysis.　The　finite　element　model　of　the　rigid　bracing　dome　was　built　by　the　truss　elements　and　cable　elements.　Through　adopting　the　block　Lanczos　modal　analysis　method,　modal　characteristics　of　the　structure　under　different　loads　condition　are　analysed.　The　influences　of　structural　parameters,　such　as　initial　prestress,　span,　load,　etc.　on　the　structural　natural　frequencies　is　concluded.　The　analysis　of　numerical　example　indicates　rigid　bracing　dome　appear　similar　or　identical　to　the　size　of　the　frequency　of　and　mutual　symmetry　vibration　mode,　whose　natural　frequency　is　small　and　intensively　distributed;　Equal　division　of　ring　direction　and　bar　section　area　have　little　influences　on　the　structural　natural　frequencies;　Under　the　action　of　load,　structural　natural　frequencies　become　smaller;　Prestress,　span,　rise　have　larger　influence　on　the　structural　natural　frequencies,　which　should　give　full　consideration　in　the　structural　design　stage.　©,　2015,　Science　and　Technology　Periodical　Press.　All　right　reserved.