Abstract: Dynamic responses of vertically vibrating pile were investigated under the axisymmetric condition.A simplified model to study the vertical vibration of pile installed in double layered saturated soil was founded firstly.Then an analytical solution in frequency domain and a semi-analytical solution in time domain were derived.The effects of frost and thaw on the complex stiffness of vertically vibrating pile were analyzed.A viewpoint was proposed that it should be based on the most disadvantageous situation for the dynamic foundation design in permafrost or seasonally frozen regions.For the permafrost,and for the seasonally frozen ground it should be based on the low limit of permafrost and on the unfrozen soil respectively.For the construction of foundation in the permafrost,the frozen soil should be maintained in its original state as rigorously as possible.Finally,the influence of the frost action on the pile test was illustrated.