In order to explore the influence of shield underpass expressway on the existing parallel channel bridges, a three-dimensional finite element model is established to analyze the influence law of shield construction on the surface settlement, highway subgrade and existing parallel channel bridge pile foundation under the background of the shield tunnel crossing the embankment of the G78 Shankun expressway in the follow-up optimization project of the Hanjiang-Rongjiang-Lianjiang river system. The results show that:1) The influence range of shield tunnel excavation on the stratum is roughly 4 times of the tunnel diameter;2) The maximum surface settlement value directly above the tunnel axis reaches 5.6mm , and the maximum settlement value of the roadbed occurs directly above the tunnel axis, which is about 5mm ;3) The vertical displacement of the pile foundation of the channel bridge is all subsided, and the settlement of the pile foundation near the shield side is greater than that of the far side, and the settlement value of the pile foundation Z1 is the largest, reaching 2.4mm ;4) The horizontal displacement of the pile foundation corresponding to the top surface of the tunnel buried depth is large, and the horizontal displacement of the pile foundation Z1 is the largest, about 0.37mm , which is affected by the superposition of shield;5) The maximum value of bending moment appears near the buried depth position of the tunnel, the maximum value of axial force appears at the midpoint position of the pile body, and the bending moment and axial force of the pile foundation Z1 are the largest.