In　this　paper,　the　modal　experiment　analysis　and　FEM　(finite　element　method)　simulation　of　a　ring　truss　structure　which　modeled　a　large　deployable　antenna　are　carried　out.　First,　an　experimental　model　for　the　large　deployable　antenna　astromesh　is　designed　and　manufactured.　And　the　experimental　modal　analysis　of　the　ring　truss　under　the　free　boundary　condition　is　conducted　by　using　hammer　method.　Based　on　the　experiment　results,　the　first　six　order　natural　frequencies,　and　the　first　six　order　mode　shapes　are　obtained.　And　the　MAC　(Modal　Assurance　Criterion)　is　introduced　to　verify　this　experimental　results.　Secondly,　modal　analysis　of　the　ring　truss　structure　under　the　free　boundary　condition　is　conducted　by　using　FEM.　The　first　six　order　natural　frequencies　and　corresponding　damping　ratio　and　the　first　six　order　mode　shapes　are　also　obtained.　Finally,　the　results　between　the　experiment　method　and　FEM　are　compared.　It　is　found　that　the　error　for　the　natural　frequencies　is　acceptable　while　the　mode　shapes　show　very　good　agreement.　In　summary,　the　results　of　the　different　methods　have　good　consistency,　which　can　confirms　that　the　analysis　of　this　paper　is　feasible　and　reliable.　Meanwhile,　the　natural　frequency　and　mode　shape　of　each　order　are　obtained.　©　2017,　Editorial　Department　of　CJAM.　All　right　reserved.