Hu-Tong Yangtze River Bridge’s approach bridge adopts a 48m-long simply supported continuous beam bridge. When a train passes through this bridge at the speed of 200~250km/h, the deformation curve of the bridge is equivalent to continuous multiple excitations with a certain wavelength and a certain amplitude, the excitation frequency is near 1Hz and almost equal to the vehicle body’s natural frequency, the vehicle body resonance is easy to excite. In order to ensure the dynamic performance of 48m-long simply supported beam bridge satisfying the specified requirements, the safety and comfort of the train-bridge system during different trains passing through at different speeds were analyzed. The results showed that for the bridge, the vertical and lateral accelerations at the middle of span are lower than the limit value in the code except that the lateral acceleration at the middle of span exceeds the limit value in the code about 7% when SS8 traction double-deck passenger train passes through the bridge at the speed of 200km/h; for trains, their safety and comfort meet the specified requirements under all working conditions, so 48m-long simply supported beam bridge can ensure passenger trains safely and comfortably passing through at 120~250km/h; in addition, the characteristics of the track irregularity are equivalent to the track irregularity management level for the rank of 160km/h in China when the dynamic performance of the train-bridge system meets the specified requirements; comprehensively considering the analysis results and the level of railway operation and maintenance in China, the track irregularity management value for the rank of 160km/h is recommended as the track irregularity management criterion of this train-bridge system.