Abstract: As for the tunnel portal section, it is characterized by steep slope, weak and fractured surrounding rock, which is easy to lead to the instability or insufficient strength of the slope. In this paper, based on the portal construction at the Dongchuan end of Yankou tunnel, the 3D finite element software is used to simulate the slope stability, the influence of sheet-pile reinforcement and tunnel excavation on the slope stability is studied, and the sensitivity analysis of the anti-slide pile support parameters is carried out. The results show that in the course of tunnel construction, the construction of portal is usually the most unfavorable stage; the stability of the slope under different working conditions is improved obviously when sheet-pile is used to reinforce the slope at the portal; with increase of embedded depth of pile, the maximum stress of pile decreases and the displacement of pile tip decreases; the impact of tunnel excavation on nearby railway can be effectively reduced by adopting sheet-pile support.