Abstract: The potential threat of earthquake disaster should be considered in the construction of subsea tunnel in offshore areas. Considering the influence of seawater hydrodynamic pressure can be more in line with the actual situation when analyzing the seismic response of subsea tunnel. A seismic analysis model of water-seabed-tunnel is established, which takes into account the nonlinearity of soil and the fluid-structure interaction between seawater and seabed. The seismic response of undersea tunnel under different seismic excitations and water depths is studied. The results show that the acoustic module can simulate the fluid-structure interaction well. Under the action of horizontal earthquake, the stress of tunnel is mainly concentrated at the arch shoulder and arch foot. The maximum hydrodynamic pressure in the calculated area under earthquake action occurs on the left and right sides of the seabed above the tunnel. Under bidirectional seismic excitation, the hydrodynamic pressure on the seabed surface increases significantly, and the stress peak at each point of the tunnel also increases significantly. The seismic response of subsea tunnel under the earthquake with rich low frequency component is much stronger than that with rich high frequency component. Seismic damage of subsea tunnel decreases with the increasing water depth. The results are of some reference value for understanding the actual seismic response law of the undersea tunnel.