Abstract: In order to discuss the behavior of piles under combined loading of vertical force V and torsion T, the paper firstly set up the governing equation of the pile shaft using the shear displacement method and pile shaft load transferring function, in which the subsoil was treated as the Gibson model and the non-coordination deformation along the pile-soil surface was considered as well. Then, both the force and displacement boundary conditions were introduced to solve the equation, generating the analytical solutions of internal forces and deformations for the pile shaft under various bearing stages of subsoil. Based on the solutions, various combined loadings of V and T were considered to determine the bearing capacity of the pile shaft, from which a V-T combined loading envelop was plotted correspondingly. The parameter analysis results show that the bearing capacity of piles under V-T combined loading increases with the pile length (L) when the aspect ratio of pile shaft (m₀) is kept constant. For a constant L, the bearing capacity of pile shaft increases with the increasing value of m₀. Furthermore, the bearing capacity of the pile shaft becomes larger as a result of increasing the stiffness ratio (λ) of pile shaft to surrounding subsoil, and\or increasing the ratio of the constant coefficient of the subsoil shear modulus distribution function to that in the ultimate friction resistance distribution function (n). The vertical force capacity of pile decreases as the torsion at the pile top increases gradually, and the drop in vertical force capacity becomes less significant with the increasing of the torsion.