In　order　to　study　the　effectiveness　of　L-shaped　bracings　in　stability　of　long-span　CFST　truss　arch　bridges,　the　mechanical　behavior　and　the　stability　of　long-span　CFST　truss　arch　bridges　are　analyzed　and　compared　through　theoretical　analysis　and　numerical　calculation　based　on　Hejiang　River　Third　Bridge.In　addition,　the　significance　of　L-shaped　bracings　in　the　stability　of　truss　arch　bridge　is　checked　by　orthogonal　test　and　multi-factor　variance　analysis　methods.The　results　show　that　(1)　for　the　topology　optimization　types　of　L-shaped　bracings,　the　main　arch　has　the　best　stability　when　the　K-shaped　diagonal　bracing　is　set　at　the　top　chord　of　main　arch　rib　and　close　to　arch　foot;　(2)　compared　with　the　K-shaped,　X-shaped　or　double-cross-shaped　bracings,　the　L-shaped　bracings　may　have　less　influences　on　the　maximum　value　of　axial　force,　in-plane　bending　moment,　out-of-plane　bending　moment,　stress　and　the　vertical　deformation　of　the　main　arch,　but　they　may　affect　the　horizontal　deformation　of　the　main　arch　to　some　extent.(3)　When　the　parameters　are　within　the　reasonable　ranges,　the　replacement　of　K-shaped,　X-shaped　or　double-cross-shaped　bracings　with　the　L-shaped　bracings　may　not　significantly　reduce　the　stability　of　bifurcation　buckling　and　the　extreme-value　point　of　the　long-span　CFST　truss　arch　bridges.Hence,　the　L-shaped　bracings　can　be　chosen　by　engineers　in　the　stability　design　of　such　arch　bridges　without　no　special　emphasis.　©　2020,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.