Abstract: To study the influence of steel pipe isolation pile on metro underground-excavated tunnel side-passing pylon in soft stratum, Chengdu Metro Line 3 Phase Ⅲ engineering of mined interval tunnel side-passing pylon is taken as example, FLAC3D finite difference software is adopted to dynamically simulate the construction of mined tunnel in soft stratum. From aspects including ground surface subsidence, pylon foundation vertical displacement and inclination, pylon structure internal force, the influence of isolation pile reinforcement is analyzed, and the reinforcement effect is evaluated with field measured data. Research results show that the steel pipe isolation pile can significantly reduce the surface subsidence, pylon foundation vertical displacement and pylon structure internal force.