A full-size nonlinear numerical model for a track-subgrade-foundation coupled system was established in this paper. In the model, the nonlinear stress-strain relationship for soil material, influence of static stress state after subgrade construction on subsequent dynamic computation, and dynamic interaction between reinforced concrete base and upper layer of formation were considered, the construction process of a track-subgrade system was simulated. Results show that a more reasonable spatial vibration response of rails can be obtained by using a solid element to simulate the rail than using beam element. Vertical dynamic displacements at the bottom of each layer of subgrade simultaneously vary with time and space. In transverse direction of the subgrade, the maximum vertical dynamic displacement at different moments within the width range of track slab is about 0.04 mm, and can be regarded as uniformly distributed. Distributions of vertical dynamic displacement along the depth at different times are similar, and the maximum value is about 0.8 mm according to the exponential function attenuation, less than the standard of 3.5 mm allowed in Chinese high-speed railway. In the longitudinal direction of the railway, the locations of peak value of vertical dynamic displacement correspond to the spatial location of applied moving loads. Distribution patterns of vertical dynamic displacement at the same depth are similar at different times. Overlap effects induced by adjacent loads corresponding to the front and rear wheelset on the same bogie are noticeable above the bottom of the lower layer of formation.