Focusing　on　the　key　problem　which　obstructs　the　span　increase　of　RC　arch　bridges,　based　on　the　composite　structure　with　steel　truss　webs　and　stiffened　skeleton　construction　method,　a　new　composite　structure　with　steel　truss　webs　and　SRC　(Steel　Reinforced　Concrete)　flanges　is　proposed.　Taking　Wanxian　Yangtze　River　Bridge,　the　longest　span　(420m)　RC　arch　bridge　in　the　world　＇using　stiffened　skeleton　construction　method,　as　the　prototype,　a　trial　design　of　composite　arch　bridge　with　steel　truss　webs　and　SRC　flanges　is　conducted.　The　result　shows　that　the　trial　design　can　satisfy　the　requirements.　The　structural　behavior　of　the　innovative　arch　bridge　is　similar　to　that　of　the　original　concrete　arch　bridge,　but　the　self-weight　is　reduced　about　25%.　The　application　of　the　composite　structure　in　long-span　arch　bridges　could　produce　considerable　weight　saving　and　facilitate　construction　methods.　It　seems　feasible　for　practical　application.