Based on the analysis of ballastless track with floating plate structure, according to the characteristics of prefabricated floating plate structure, a mechanical model of continuous integral floating plate structure, namely the Bernoulli-Euler beam model with elastic support, is established. Through the analysis of the influence of different longitudinal arrangements of the continuous floating plate structure on the vibration response of the rail girder system, it is concluded that when the length of the continuous floating plate is twice the span of the box girder, the displacement, acceleration, and dynamic disturbance and acceleration values of the box girder are relatively small. In the initial design of the floating plate ballastless track, it is suggested that the length of the continuous floating plate can be twice the span of the box girder.