Abstract: With the hypothesis of “Beam-on-Dynamic-Winkler Foundation”, the motion equation of the passive pile is established in studying the vertical interaction of two piles, and the closed-form solution of dynamic interaction factor in homogeneous soil deposits is obtained. The differential equations of single pile for vertical vibration in different soil layers are established. According to the continuity condition of pile between different soil layers and the boundary conditions at the pile top and bottom, the solution of the differential equations can be obtained. A three-step method for calculating the dynamic interaction factors of the pile embedded in layered soils is proposed. Then the impedance of single pile and the dynamic interaction factors are used to calculate the vertical and rocking impedance of pile groups. Through theoretical analyses of practical problems, some useful results are obtained and conclusions are drawn.