Abstract: The vibration response of offshore large-diameter pipe piles subjected to harmonic horizontal dynamic loads is studied by considering the pile-soil-seawater coupled vibration. The governing equations for the outer and inner seawater are established, and the analytical expressions for the velocity potential of the seawater are obtained, then the expressions for the hydrodynamic seawater pressure acting on the pile body are obtained. Considering the soil as the viscoelastic medium, the governing equations for the outer and inner soil are established. The coupled equations are directly solved, and the expressions for the displacement and resistance of the outer and inner soil are obtained. By using the displacement continuous condition at pile-soil interfaces, velocity continuous condition at pile-seawater interfaces and boundary conditions of piles, the analytical solution for the displacement of the offshore large-diameter pipe piles under horizontal dynamic loads is obtained, and the horizontal dynamic compliance factor of pile top is defined. The solution is compared with the FEM results to verify the correctness. The effects of hydrodynamic seawater pressure, length of pile embedded in seawater, outer and inner pile radii, pile modulus and soil modulus on the horizontal dynamic characteristics of offshore large-diameter pipe piles are analyzed.