Taking the shield tunneling under a high-speed railway simply supported girder bridge as the engineering background, the finite element software Midas/GTS is used to establish a shield tunnel underneath the high-speed rail bridge model to analyze the dynamics of the high-speed railway simply supported bridge under the shield tunneling and train load response. The research first analyzed the impact on the settlement of the high-speed railway simply supported beam bridge pier top when the shield was excavated to the near side of the bridge and the train was running at different speeds of 200-350km.h-1 and different axle loads of 110-220kN. Next, the deformation laws of high-speed rail bridge piers and abutments under different excavation stages under the impact of the dynamic load of the train with a speed of 200 km.h-1 and an axle load of 110 kN are discussed. The results show that when the shield is excavated to the near side of the bridge, the deformation of the top of the high-speed rail bridge pier and abutment is basically the same under the impact of different speeds and axle loads. The settlement reaches the peak in a certain period of time, and then rapidly decreases and stabilizes at a certain level. Within a fluctuation range; with the increase of train speed and axle load, the peak settlement of the pier and abutment will increase; during shield excavation, the settlement of the pier and abutment when the train speed is lower than 200 km.h-1 and the axle load is less than 110kN When the peak value meets the vertical settlement control standard of a single pier top of a high-speed rail bridge, compared with the train speed, the train axle load has a greater impact on the dynamic response of the bridge; Under the action of dynamic train load, the impact of shield tunnel excavation on the deformation of high-speed rail bridge pier top is mainly from shield excavation to the initial excavation stage near the bridge. The deformation of the pier top after shield excavation is far from the bridge side is basically in a stable state .