In order to investigate the impact of bridge dynamic response on train derailment risk, the three-dimensional numerical models were established using finite element software ANSYS/LS-DYNA to numerically simulate the entire process of ship collision on the bridge. The influence of different impact velocities on the dynamic response of the bridge under impact force was studied. Based on the numerical simulation results, a lateral acceleration of 1 m/s² on the bridge deck was used as the external excitation limit, to evaluate the derailment probability of trains traveling on the bridge. The results indicate that as the impact speed increases, the peak impact force, lateral displacement of the smain tower, and lateral acceleration of the bridge increase accordingly. The impact speed has a significant impact on the ship collision dynamic response and the probability of train derailment; When the impact speed is 2.5 m/s, the maximum lateral acceleration on the bridge deck is 0.942 m/s², which does not exceed the critical limit of train derailment acceleration by 1 m/s², and there is no risk of derailment. When the impact speed is 3.5 m/s and 4.5 m/s, the probability of train derailment is 1.371 × 10^-6 and 1.920 × 10^-6. The research conclusion of this study can provide reference for the analysis of bridge ship collision dynamic response and the risk assessment of train derailment on the bridge.