The non-linear finite element equilibrium equation based on the contact interface is build by the finite element method of sub-structure using cohesion degree of freedom, contact constraint which is dealt with by the augmented Lagrangian multiplier method, and pile-soil interaction effect was calculated by nonlinear numerical calculation. Results show that the general trend of numerical results and the measured results are the same. The introduction of the contact problem can reasonably explain the mechanism of pile-soil interaction effect.