Abstract: In order to ensure the good quality of the dynamic behavior of a large structure to be built, it is advisable to identify the modal parameters of its scaled model in advance. Then, using the prediction equations, the identified parameters can be convert to that of the prototype and predict the dynamic behavior of the real structure. This paper gives a brief review of dynamic similitude principle as an introduction. The main purpose is to derive the design equations and the prediction equations of the scaled model used in vibrational modal analysis. And the conversion relationships of the modal parameters between model and prototype were deduced. As an example, the model design conditions and the experimental conditions of a component of a large scale excavator were determined.