A perfect two and half dimensional (2.5D) finite element-boundary element coupling model is established to analyze vibration responses of the rails, fasteners, sleepers, ballast, embankment and ground under moving harmonic load. Vertical dynamic wheel-rail forces due to track vertical irregularities with harmonic amplitudes are gained by using the existing analytical model for vertical vibration of the vehicle-track-embankment-ground coupling system. On this basis, a computation method for power spectrum of ground vibration from train is proposed by considering the power spectra densities of track random irregularities. The theoretical calculation results and the corresponding experimental results of vertical acceleration levels for ground surface points are compared, and the model proposed in this paper is validated. The proposed model can effectively analyze vibration responses of the track-embankment-ground system with complex cross-sectional shapes, and also can analyze influences of a variety of vibration reduction and isolation measures. This model has high computation efficiency, and is applicable to compare design schemes of the railway line.