Over recent years, high-speed and heavy-load railways have developed in China. For a railway line, bridges are very important hubs along the line. Studies on the interaction between trains and bridges are very important for safe railway operations, especially for problems regarding the train-bridge coupled vibration of simply-supported steel-truss railway bridges, which have been widely used in recent years. In this paper, a 156-m-long simply-supported steel-truss bridge of the Huang Han-hou New Yellow River railway was studied. Numerical simulation using ANSYS and UM software is used together to study the train-bridge coupled vibration problems when a single locomotive, marshaling passenger coach, and freight coach pass the bridge. The results show that the lateral stiffness of the large-span steel-truss bridge is relatively small. The dynamic response parameters of the train and bridge all fell within the allowable limits when the different marshaling passenger coaches pass the bridge with the design speed. Compared with conditions of a single locomotive and marshaling passenger coach, the lateral and vertical accelerations of the bridge are obviously greater when the marshaling freight coaches pass.