In order to study the response law of track bed and subgrade when shield tunneling under high-speed railway subgrade, based on the actual project of Xi"an Metro Line 1 under Zheng Xi"an high-speed railway, the upper subgrade settlement caused by double track tunnel construction is estimated based on the settlement theory, the numerical model of interval tunnel under existing high-speed railway subgrade is established, and the track bed, subgrade Vertical settlement of CFG pile and stress response law of CFG pile. The results show that the axial force of CFG pile, the vertical settlement deformation of track bed and subgrade increase with the gradual increase of the clear distance between the pile bottom and the tunnel, and reach the maximum when the construction is directly above the tunnel. The settlement decreases with the increase of the horizontal distance from the tunnel parallel to the excavation direction, and increases gradually along the shield construction direction. The track bed and subgrade structure incline, but the vertical inclination height is not more than 2mm; The maximum axial force of CFG pile group foundation is concentrated on single piles on both sides, while the axial force of CFG pile directly above the tunnel is small. Under the working conditions of h = 3.235m and 5m, the axial force of CFG pile reaches the minimum and maximum, and the CFG pile within the cushion layer does not suffer compression failure.