Abstract: In order to investigate the coupling interaction between high-speed train and extradosed cable-stayed bridge as well as the dynamic performance of extradosed cable-stayed bridge, a (34+118+240+118+34) m Yuanjiang extradosed cable-stayed bridge of the newly built Changyichang Railway is considered as the engineering background, and the vibration characteristics of the coupled system of the train and the bridge are investigated using field measurements and numerical simulations. The dynamic experiment is conducted to test the dynamic response of the bridge structure with respect to strain, deflection, and acceleration when the dynamic load comprehensive rail inspection vehicle passes through the bridge at different speeds. A coupled vibration model of the train-bridge is established. Moreover, the reliability of the coupled vibration model is confirmed by comparing the numerical simulation and dynamic experiment results. On this basis, the effects of different speed conditions on the dynamic response of the train-bridge coupling system and the indicators of train running safety and stability are investigated. The results show that: the numerical simulation results of the dynamic response of the bridge are basically consistent with the measured results, and the indexes safety and stability of train under the design speed meet the specification limits. The maximum measured dynamic coefficient of bridge structure is 1.16, and the bridge structure has good lateral and vertical stiffness and dynamic properties.