To　investigate　the　seismic　response　characteristics　of　low-gravity-center　cable-stayed　bridges　with　twin　towers,　a　simplified　mechanics　model　was　established　based　on　the　transmission　path　of　the　horizontal　seismic　inertial　forces　of　the　girder　under　earthquake　excitation.　The　definition　of　a　low-gravity-center　cable-stayed　bridge　with　twin　towers　was　proposed.　Two　1:75　scale　models,　a　floating　system　(FS)　cable-stayed　bridge　and　a　fixed-hinge　system　(HS)　cable-stayed　bridge,　were　fabricated,　and　shaking　table　tests　were　conducted.　The　results　of　these　tests　showed:　(1)　horizontal　cracks　appeared　at　the　bottom　and　middle　areas　of　the　main　tower　in　the　Test　Model　FS,　whereas　diagonal　cracks　together　with　concrete　spalling　formed　at　the　bottom　area　of　the　main　tower　and　the　bottom　crossbeam　in　the　Test　Model　HS;　(2)　the　Test　Model　FS　experienced　a　larger　displacement　response　but　a　smaller　acceleration　response　compared　to　the　Test　Model　HS;　and　(3)　the　reinforcement　strain　response　at　the　bottom　of　the　main　tower　of　the　Test　Model　HS　is　smaller　than　those　of　the　Test　Model　FS,　which　is　in　good　agreement　with　the　theoretical　analysis　of　the　low-gravity-center　cable-stayed　bridges.　In　general,　the　fixed-hinge　system　cable-stayed　bridge　can　reduce　the　overall　structural　damage　under　strong　earthquakes　and　is　therefore　suggested　to　be　used　in　low-gravity-center　cable-stayed　bridges.　The　research　results　help　to　understand　the　failure　characteristics　of　the　cable-stayed　bridges　and　to　provide　a　reference　for　the　seismic　design　of　low-gravity-center　cable-stayed　bridges　in　practical　engineering　applications.