Due to the existence of a deep seawater layer in marine sites，its influence on the seabed ground vibration characteristics and the seismic response of marine structures is significant and should not be ignored in the seismic analysis of marine structures such as cross-sea bridges. Therefore， to determine the influence of the seawater layer on the seismic response of the structure， the study establishes the seismic fluctuation analysis model based on the seismic fluctuation theory for the coupled seawater-seabedstayed bridge. In addition， considering that the marine environment may pose a threat to the durability of the damping members， the study proposes a new type of cable-stayed bridge damping system using Bulking Restrained Brace（BRB）with excellent durabili‐ ty as the longitudinal damping member， and takes the Qingzhou Channel Bridge as the engineering background to verify the seismic response by comparing it with the floating system cable-stayed bridge model. The feasibility of the new type of seismic damping system considering the influence of the marine environment is verified. The study optimizes the location and equipment parameters of the BRB. The design method of BRB as a longitudinal damping member for cable-stayed bridge is further determined. It is found that the hydrodynamic effect generated by seawater under the seismic action will amplify the seismic response of the super‐ struc‐ ture of the cable-stayed bridge. By comparing the seismic response of the structure under different working conditions， it is con‐ firmed that the best overall seismic damping effect of the bridge is achieved when the BRB is installed at the pier and tower loca‐ tions simultaneously. Besides， the parameters such as yield bearing capacity of BRB also have a great influence on the seismic per‐ formance of cable-stayed bridges.