Based on the dynamic winkler-foundation beam model and interfacial transfer matrix scheme

the explicit expressions indicating force-displacement relationship of piles are derived under combinative axial and lateral loads in layered-soil. In terms of the improved Gazetas’s three-step procedure for pile-soil-pile interaction in homogenous media

a new method for calculating dynamic interaction factors for strata-soil is suggested under harmonic excitation. A relatively concise scheme to horizontal dynamic effect on pile-group considering the influence of axial load is expatiated. The vibration characteristic including frequency-dependent displacements and internal forces of pile-group could be also roundly revealed by the presented method.