Abstract: Based on the case study of Lanzhou Metro Line 1 crossing the Yu′ergou Bridge, the indoor model is built according to the pile foundation underpinning design plan, and the variation law of vertical displacement, pile axial force and side friction resistance of piles before and after replacement is studied. The results show that the settlement value of the pile group foundation is 0.34 mm when the No.3, No.4, and No.5 piles are cut until stable settlement. When the tunnel excavation is simulated and the lining is constructed until the settlement is stable, the pile group foundation sinks 0.53 mm, indicating that during underpinning process, the influence of tunnel excavation is greater than pile cutting on pile group foundation deformation; after pile cutting, the pile top axial forces of No.1, No.2, No.5, No.6, and No.7 piles increase by 35.88% and 54.00%, 36.00%, 43.67% and 26.23% respectively; the axial forces of No.5 and No.6 piles are distributed in an inverted trapezoid shape, and the axial force and side friction resistance of the pile gradually increase with the increase of the upper load. After pile cutting, the side friction resistance of upper part of No.5 and No.6 piles increases significantly while bearing the upper load. When the upper load is 50 kN and 76 kN respectively, the side friction resistance of No.5 and No.6 piles decreases drastically, and shear failure occurs at the pile-soil interface.