Abstract: The longitudinal seismic response analysis of immersed tunnels is crucially important for the seismic design of immersed tunnels. Using the geometric features and structural characteristics of immersed tunnels, a dynamic model composed of multi-rigid bodies, elastic damping hinges, and damping hinges is proposed for immersed tunnels based on reasonable assumptions. The mathematical models and formulae are deduced using the discrete time transfer matrix method (MS-DT-TMM) of multibody dynamics theory. The new method is applied to a reference dynamic test and the seismic response of an immersed tunnel is analyzed. Results using the proposed method compare well with benchmark simulations from the traditional finite element method. The research could provide references for the rapid calculation of seismic response in immersed tunnels.