Research of the pile-soil interaction effect is a complicated issue in civil engineering. Using the principle of soil dynamics and structural dynamics, a simplified computational method for computing the lateral dynamic impedance of single pile embedded in layered non-homogeneous subsoil is established based on a certain assumptions. Both non-homogeneity of soil strata and softening effect of soil layer around pile during vibration as well as separation of pile-soil interface are simultaneously taken into account in the proposed computational method. The characteristics of the frequency-dependency of lateral dynamic stiffness and damping of pile are reproduced. It is shown through the comparative study on a numerical example that the numerical results of dynamic impedance of pile computed by the proposed method are relatively rational and can well agree with the computational and experimental results currently available.