When a subway shield tunnel passes through an existing railway bridge on the side, it will have varying degrees of impact on the bridge pile foundation, and different angles of passing will cause different deformations in the soil and bridge piles within the intersection range of the two. Based on the construction of a shield tunnel under a railway bridge in the northern section of Tianjin Metro Line 4, a three-dimensional numerical analysis model of the tunnel soil pile foundation bridge system was established. Combined with actual engineering measurements, the impact of tunnel excavation on the bridge pile foundation was analyzed for four lateral crossing conditions at angles of 85°, 80°, 76°, and 70° between the tunnel and the railway bridge. The results indicate that changes in the crossing angle will have varying degrees of impact on the deformation and stress of bridge pile foundations. The smaller the crossing angle, the greater its impact on the deformation of bridge piles, and there exists an optimal crossing angle. When the optimal crossing angle of 90° cannot be selected in practical engineering, se-tting isolation piles between the tunnel and bridge piles for reinforcement can effectively reduce surface settlement and pile foundation deformation, thereby protecting the existing bridge.