Railway bridge is an important foundation structure of the train running line, when the train passes through the line, it will produce large vibration, and the water supply pipeline under the railway subgrade will resonate due to the passing of the train, resulting in pipe rupture and corrosion and other adverse consequences. Therefore, based on the fluid structure interaction analysis method, the velocity and pressure distribution of the pipeline were analyzed by using RNG κ-ε turbulence model; the natural frequencies and vibration modes of the pipeline under the free state and the unidirectional fluid structure interaction were compared. The results show that the flow velocity in the pipeline is symmetrically distributed along the central axis of the pipeline, the water flow presents a spiral encircling trend, and the turbulence phenomenon appears at the bend of the pipeline; the natural frequency difference between free state and unidirectional fluid structure interaction is 8%~10%; the maximum deformation of pipeline in free state is 0.429 m, which is 5% higher than that under unidirectional fluid structure interaction.