Abstract:  Under a harmonic moving load, according to the characteristics of periodic structural dynamic responses, the problem that the dynamic response of the infinite floating slab track (FST) is transformed to be solved within the track range corresponding to one floating slab. Then through the displacement influence matrix of the floating slab, the coupling of the rail and the discontinuous slab is implemented in the frequency domain, and the dynamic response of rail in the range is obtained. Further, based on this, the dynamic response at any point on the track structure is obtained. The calculation results show that: Under the harmonic moving load, the displacement response spectrum’s peak of FST appears near the excitation frequency of the moving load; with the increase of the loading velocity, there will be a decrease on the displacement response spectrum in a very narrow frequency band around the excitation frequency of the moving load, while there will be a significant increase in most of other frequency bands; when the excitation frequency of the moving load is equal to the nature frequency of FST, the resonance occurs, the displacement response spectrum’s peak is much larger than those under other excitation frequencies; due to the moving load periodically pass through the discontinuous slabs and the fasteners, there exists a parametric excitation; when the load excitation frequency is close to the frequency of the formation of standing waves due to the slab’s discontinuity, the track structure will also have a greater displacement response.