Based on the three-dimensional continuum theory of viscous damping soil and the radial annular complex stiffness transfer model，a simplified analytical model for torsional vibration of piles in viscoelastic soil is established by considering the effects of both radial and longtudinal inhomogeinety of surrounding soil. The solution of torsional vibration displacement of surrounding soil is obtained by using Laplace transform and complex stiffness transfer method，then the form is coupled into the dynamic balance equation of the pile by using the complete coupling condition of pile-soil，and the analytical solution of torsion impedance of pile top is derived by the method of torsional impedance transfer. Furthermore，the obtained analytical solution for torsional impedance at the top of pile is degraded and compared with the existing solutions to verify its rationality. Based on that，an extensive parametric analysis is also conducted to discuss the influence of the disturbance degree，disturbance range of surrounding soil，necking and expanding of pile on the torsional impedance at the top of pile，which can provide reference and guide to related engineering practice.