A problem in the application of similarity theory in the structural dynamics model test is discussed, in order to study the accurate prediction method of the dynamics in the actual structure through similarity theory and scale model test results. First, considering actual engineering test conditions, the geometry and physical parameters similar ratio are fixed, and the similarity relationship between the natural frequency response and time domain response is derived from the actual non-geometric scaling model, based on the similarity theory and the finite element method. Then, the accuracy of this similarity relation and engineering value is verified through the sheet structure vibration test. Finally, theoretical derivation and test results prove that the similarity of the dynamics from the above derivation can accurately predict the dynamics characteristics of the actual structure, according to the scale model of dynamics.