With the rapid development of rail transportation in China, high-speed and heavy-load railways have become the trend of development in this field. In such systems, it is important to consider the interaction process between the train and the bridge, along with the influential factors, when a train passes through a bridge. In this paper, a 156-m long simply-supported steel truss bridge of the Huang Han-hou New Yellow River Railway is taken as an example. A dynamic model of the train-bridge was constructed considering a wheel-rail relationship. Serpentine movements and track irregularity were used as self-excited excitation sources of the train-bridge system. The finite element software ANSYS and UM (Universal Mechanism) were used to simulate the train-bridge coupled vibrations. The influence of the bridge structure of the portal frame, wide-span ratio, curve of the steel truss and track irregularity, as well as the marshaling coaches on the train-bridge coupled vibrations were discussed with the numerical simulations. The results showed that the gantry of the steel truss bridge had greater influence on the acceleration. As the line radius of the curved steel truss bridge increased, the dynamic responses of the train became smaller, thus affecting wheel-rail force. Moreover, with increasing wide-span ratio, the lateral stiffness of the bridge increases, and the bridge lateral vibration became smaller. When the track conditions became worse, the dynamic responses of the train increased considerably and the comfortable and stability worsened. The findings indicate that the full empty grouping and empty-weight mixed grouping schemes are harmful to the coupled system of a train-bridge, which should be avoided in practical operation.