Abstract-In this paper, we take the railway subgrade dynamic response test system as the study object, the laboratory test reaction frame's model factors were analyzed through the finite element analysis software MSC.Patran/Nastran. The former six-order original frequencies and vibration modes of the frame were caculated and evaluated in detail. Then we studied its transient response under two working conditions: when it's fully loaded and suddenly unloaded, and the deformation displacement curves of the key points of the frame were obtained. These results provide a basis for the detailed study to the mechanical behavior of the frame and setting the proper working frequencies of the hydraulic servo excitation cylinder to avoid the resonance.