Abstract: Assuming that soil is uniform and linear viscoelastic layer with viscous damping, soil-pile interaction and the frequency-domain torsional response of a dynamically loaded pile in the soil layer are theoretically investigated. By Laplace transformation, the soil layer is studied first and the vibration displacement solution with undecided constants of soil layer is used in the analysis of pile response. And the corresponding solution of the displacement and velocity response functions at the pile head in frequency domain and the dynamic stiffness of pile are obtained in closed forms. A parametric study is conducted to determine the main features of the soil-pile interaction, and the special influence of viscous damping of soil layer is also discussed. Finally, a comparison between the theories based on plane strain assumption and the solution developed in this paper is investigated.