Considering that existing shaking table tests on bridge structures have not taken into account the effect of moving trains, this paper takes a multi-span simply supported girder with a CRTSII slab ballastless track system and a Chinese CRH2C high-speed train as its objects of study, builds a reduced-scale model for the bridge and train using a similarity ratio of 1:10, and constructs an on-bridge running test platform based on a four-array shaking table. A running test under seismic action is preformed to explore the effects of train speed and the vertical component of ground motion on structural responses under the combined action of seismic and train loads. According to the findings of this paper, a higher train speed leads to more intense wheel-rail interactions. Train speed and the vertical component of ground motion have significant effects on the vertical deformation of structures and on the transverse deformation of bearings and piers, but their effects on the transverse deformation of track structures are negligible. The vertical component of ground motion may cause vertical separation between girders and bearings. The train may induce disengaging between track structures in the vicinity of girder gaps.