In order to consider the dynamic responses of track and subgrade of the scaled track-subgrade model and the interaction between them, a uniform dynamic similitude method for the track-subgrade system was first proposed. The dynamic similitude design of the track was conducted and the acceleration-scaling factor of the track-subgrade model was assigned as 1.0. Then, the track and subgrade follow the same length scaling factor and the shear wave of the subgrade model was controlled to perform the dynamic design of the subgrade structure. By using the proposed approach, the similitude design of a 1/4-scaled track-subgrade model system was conducted and a series of dynamic tests of the model system under the excitations with different frequencies were carried out. The acceleration responses of different positions of the model were measured and analyzed. The first-order frequency of the test system was obtained. The results show that there exists time delay in the process of downward transfer of acceleration. Under the excitations with a certain frequency, the characteristic frequencies, which were obtained by using the spectrum analysis of acceleration, of different structural layers are consistent.