The horizontal vibration of the pipe pile groups in saturated soil is studied by considering three-dimensional wave effects on the saturated soil

and the horizontal dynamic impedance of pipe pile groups is also obtained. The soil around pile and pile core soil are considered as two-phase saturated soil

and the mechanical property of the saturated soil is described by the theory of porous medium. The horizontal dynamic impedances of the saturated soil around pile and in pile core are obtained by using the mathematical physics means. Using the wave spread theory and superposition principle

the horizontal force of any pipe pile is obtained by considering boundary conditions and orthogonality of trigonometric functions. The horizontal dynamic impedances of pipe pile groups in saturated soil is obtained by considering the displacement compatibility conditions and horizontal force equilibrium conditions at pipe pile top at rigid cap. The influences of physical parameters on the dynamic characteristics of pipe pile groups in saturated soil are analyzed and discussed by using 2×2 pipe pile groups as an example. The result indicates that there are some differences between the horizontal dynamic impedances of the solid core pile groups and the pipe pile groups. It needs to consider the influence of the difference between the saturated soil around pile and in pile core on the dynamic impedance of pipe pile groups in saturated soil. Length to diameter ratio and wall thickness of pipe pile have great effect on the horizontal vibration of pipe pile groups in saturated soil

showing that the size of pipe pile should be focused in the actual engineering design.