To　reduce　the　heavy　self-weight　and　simplify　the　construction　process　of　concrete　arch　bridges,　a　new　type　of　structure　of　concrete-steel　truss　web　arch　was　proposed,　which　are　composed　of　concrete　upper　and　lower　flanges　and　steel　truss　web　members.　The　Wumengshan　Bridge　is　the　first　such　composite　arch　bridge,　which　is　under　construction.　UHPC　has　good　durability　and　corrosion　resistance　and　higher　strength　than　conventional　concrete,　the　self-weight　of　such　composite　arch　can　be　furtherly　reduced　If　UHPC　is　used　to　replace　conventional　concrete,　and　the　service　life　od　arch　bridge　can　be　extend,　which　has　significant　economic　benefits.　To　investigate　the　mechanical　behavior　of　UHPC-steel　truss　web　composite　Arch　Bridge,　a　trial-design　on　such　composite　arch　bridge　is　carried　out　based　on　the　prototype　of　the　Wumengshan　Bridge.　The　trial　design　results　show　that　the　sectional　dimensions　of　arch　rib　can　be　greatly　reduced　using　UHPC.　Compared　with　concrete-steel　truss　web　composite　arch　rib,　the　dead　load　of　UHPC-steel　truss　web　arch　rib　can　be　reduced　by　20.9%.　The　bending　moment　and　axial　force　at　the　arch　seat　were　reduced　by　22.1%　and　35.9%,　respectively,　and　those　at　the　vault　were　reduced　by　21.2%　and　61.3%,　respectively.　The　horizontal　thrust　at　the　arch　seat　was　reduced　by　21.2%.　©　The　Author(s),　under　exclusive　license　to　Springer　Nature　Switzerland　AG　2025.