Abstract: The mechanical properties, especially dynamic behaviors of the pile in saturated soil and single-phase soil are significantly different due to the flow quality of pore water in saturated soil and the difference in the porosity of soil and pile. The vertical impedance of saturated soil and the attenuation function of displacement of free field were obtained by using layer method and potential functions. The interaction of pile to pile and the vertical impedance of pile groups in saturated soil were investigated. The results indicated that the distance between piles, force factor of fluid phase and solid phase, modulus ratio of pile and soil affected vertical dynamic impedance of pile groups in saturated soil. The study of the pile in saturated soil provided significant help for dynamic inspection and design of pile.