Extradosed cable-stayed bridges possess structural properties of both girder bridges and cable-stayed bridges, and the advantages of aesthetic appearance and high stiffness. Therefore, Applications of the extradosed cable-stayed bridge in urban rail transit are gradually increasing. However, there are few studies on the dynamic performance of extradosed cable-stayed bridges in urban rail transit under train load. Taking an extradosed cable-stayed bridge with the maximum span among its type of bridge in China, that has been completed and opened to traffic as the engineering background, field measurement campaign including ambient vibrating test and dynamic load test are carried out to obtain the bridge modal parameters and dynamic responses of bridge main components. The bridge finite element model is established using beam elements to simulate the main girder. The bridge modal and dynamic response results obtained from field measurements are compared to verify the accuracy of the established finite element model. Based on the validated numerical model, dynamic responses of the bridge subjected to metro trains are further analyzed through the computation of the bridge displacement and acceleration responses induced by the trains with different speeds and compositions passing over the bridge. The research results show that the large-span extradosed cable-stayed bridge has good dynamic performance. Calculation results of the analysis model are in good agreement with field measurements. Additionally, as train speeds increase, both bridge displacement and acceleration demonstrate an increasing trend, especially the acceleration response.