Abstract: This paper proves that the application of a numerical simulation method is reliable for studying the influ? ence of tunnel excavation on an adjacent pile group by comparision of the two-phase method and numerical simulation method. Based on the Mohr-Coulomb elastic-plastic yield criterion, a three-dimensional numerical model was established with the finite difference numerical analysis software to study the variation law of the shielding effect of a pile group under different stress release rates, pile spacings and pile lengths. The analysis results show that the stress release caused by tunnelling has little influence on the shielding effect; the curves of the pile group shielding effect coefficient decrease with the increase of pile spacing except for the pile settlement; the influence of pile length difference on the shielding effect is more complicated, because the variation of various indexes does not exhibits the same law with changing of the pile length.