Abstract: The dynamic interactions between the saturated soil around the pile and the pipe pile, and between the pile inner saturated soil and the pipe pile were modeled by the dynamic Winkler spring-damper. In the case of ignoring the radial and circumferential displacement of pipe pile, the saturated soil around the pile was supposed be composed by the infinite thin soil layers with a round hole, and the pile inner saturated soil was regarded as be composed by the infinite circular thin soil layers, and the stiffness coefficient and damping coefficient of the dynamic Winkler spring-damper model were obtained by means of mathematics and physics. The vertical displacements of active pipe pile and passive pipe pile in the saturated soil were obtained by using the initial parameter method and the transfer matrix method, and the longitudinal dynamic interaction factor of pipe pile and pipe pile in the saturated soil was also got. Based on the principle of superposition of pile groups and the vertical dynamic interaction factor of pipe pile and pipe pile, the vertical dynamic impedance of pipe pile groups in the saturated soil was also obtained. The numerical analysis showed that:the curves of the longitudinal dynamic impedance of pipe pile groups will fluctuate more severe with the frequency when the pile spacing is bigger. The amplitude changes of the curves of the longitudinal dynamic impedance will be bigger with the frequency when the inner radius and the ratio of length to diameter are bigger, while the amplitudes will be smaller when the modulus ratio of the pipe pile and the saturated soil is bigger. The influence of pile spacing on the dynamic stiffness of pipe pile groups is the largest, followed by the ratio of length to diameter, and the modulus ratio of pipe pile and saturated soil is the smallest.