Abstract: The immersed tunnel is buried in the shallow surface of seabed, which is quite different from the land tunnel. It is of great scientific significance and engineering application value to study the seismic stability of immersed tunnel. The viscoelastic-plastic stress-strain hysteresis curve of soil was constructed based on the “extended Masing” rule, and the real-time coupled shear-volume strain increment model was taken as the source term of the change of the excess pore water pressure in Biot dynamic consolidation equation, and an effective stress analysis method was established for the liquefaction process of sand. The effective stress method was implemented based on the FLAC3D computing platform and its reliability was verified. Taking a typical borehole in Bohai sea as site condition, the seismic stability of immersed tunnel in sandy seabed was numerically simulated, and the uplift mechanism of immersed tunnel in liquefied seabed was studied. The results show that the decrease of the friction resistance of the side wall, the increase of the buoyancy of the bottom and the large deformation of seabed together lead to the uplift of the immersed tunnel. The asymmetric acceleration of the input ground motion leads to the asymmetric response phenomenon on both sides of the tunnel, and then leads to the separation of vertical displacement time history on both sides.