To study reasonable seismic design parameters of track structures, based on the theory of structural dynamics, a track dynamics analysis model considering seismic excitation sources was established. The dynamic response of CRTSⅢ slab ballastless track caused by seismic excitation was calculated. The influence of track structure parameters on dynamic response variables were studied. The findings show that the frequency of the typical earthquake waves is mainly in the range of 0~10 Hz. The three-dimensional natural frequencies of the track structure are greater than 10 Hz. The track displacement under earthquake may exceed the standard limit requirements, and the composite track slab can be connected to the base to strengthen the seismic resistance of the track structure. When the stiffness of the fasteners or the elastic modulus of the base increases, the dynamic response indicators basically increase accordingly. When reasonable matching of track parameters is ensured, appropriately reducing the stiffness of the fasteners and the elastic modulus of the base is beneficial for structural seismic design. When the stiffness of the fastener or the elastic modulus of the base changes, the lateral displacement of the track slab, the longitudinal stress of the base, and the lateral acceleration of the rail are significantly changed, which should be paid attention to during the calculation. The results can provide reference for seismic design, evaluation, and reinforcement measures of track structures.