In order to study the dynamic response of the ballast bed in the section of the ballast track foundation bed, a set of model test equipment was made to simulate the process of the railway foundation bed slurry. The subgrade model was filled with silty clay and ballast gravel, and three SmartRock sensors were embedded in different positions of the ballast layer to monitor the vibration acceleration and movement attitude changes of ballast in real time. The test results show that the vibration of ballast particles in the ballast becomes more intense after the mud invades the ballast bed, and the deepening of the mud invades the ballast bed will increase the vibration level of ballast particles. In the clean road bed, there will be a strong restraint between the ballast particles, and the ballast particles are not easy to rotate. Regardless of the track bed condition, the degree of ballast particles rotating around the transverse and longitudinal is greater than that around the vertical. When the mud intrudes into the ballast bed, the ballast particles will produce a large rotation around the transverse and longitudinal directions, and the rotation angle around the vertical has no obvious change.