With the rapid development of urban rail transit, the shield tunneling method used to construct new subways across existing high-speed railway bridges often occurs. In this paper, under the combined action of the double-track construction of a shield tunnel in a certain project and the train load, railway pile foundation from the deformation of the bridge pier and the settlement of the pile foundation. The vertical displacement distribution law analyzes the impact of shield construction and train load on the pile foundation of the existing bridge, and at the same time evaluates the safety of the bridge accordingly. The results show that the deformation of the existing bridge caused by the shield tunneling construction and the train load mainly affects the initial excavation stage. With the excavation, the settlement value gradually stabilizes, and the settlement of the bridge decreases slightly when the left line tunneling is completed. The shield tunneling of the right line has a certain compensation effect on the left line, and the overall settlement value of the bridge pile foundation is in a stable state.