With an expressway as the research background,based on engineering characteristics,geological condi-tions and design code,the finite element numerical analysis was carried out to design a large-span extradosed cable-stayed bridge.The superstructure adopts prestressed concrete partial cable-stayed bridge with span arrangement of 118 m+220 m+118 m,single box and double chamber large cantilever diagonal web wide box girder and Herringbone-shaped main tower.The cable-stayed cables are arranged in single plane fan-shaped and double horizontal rows.The tower girder pier is consolidated system.The lower structure adopts double-limb thin-wall pier and pile group founda-tion.The results can meet the needs of bridge structural stability,economic benefit control and environmental protection design.