Considering the influence of offshore ground motion and complex subsea environment on the earthquake response of seacrossing bridges，it is necessary to establish a seismic analysis model including seawater layer，seabed sites，and sea-crossing bridge. Combining finite element dynamic analysis software and wave analysis program，a novel seismic response analysis method considering pile-soil-seawater-bridge coupling is built. On this basis，A new type of energy and shock absorbing structural restraint for cable-stayed bridge is proposed. The new restraint system installs buckling-restrained braces（BRB）between the tower（pier）and the beam. A sea-crossing cable-stayed bridge is used as engineering background. According to the real site condition under sea?bed and the influence of seawater，three kinds of cable-stayed bridge that of full-floating system，with viscous damper between the tower（pier）and the beam，and with BRB between the tower（pier）and the beam are established. In the seismic wave analysis model for considering the pile-soil-seawater-bridge interaction，the strong earthquake records including the 3.11 earthquake in Japan are input. The displacement and bending moment response of bridge towers，the relative displacement and internal force of key positions，and the hysteretic curve of energy dissipation are compared between different restraint modes（viscous dampers and BRB）. The study finds that the cable-stayed bridge with viscous dampers can effectively reduce the relative displacement of the bearing and between tower（pier）and main girder. And the displacement of tower top is also well controlled，but the bending moments of the tower（pier）bottoms are significantly increased. However，the cable-stayed bridge structure setting the BRB can greatly reduce the bending moment of the bottom of towers（piers），and have a good energy consumption.