Based on the research on how to build up the model of a mechatronics control system, this paper proposed a digital measuring approach implemented with the Semi-practical Simulink system of dSPACE, which can be used to test the frequency response and identify the model of the mechatronics equipment. The optimal estimate principile of the frequency response function was deduced theoretically, the principle of selecting testing parameters was analyzed practically, and the analytic and experimental results were provided. With this approach, it’s very convenient to work out the frequency characteristic curve and the transfer function expression of the system, as well as to import the model parameters to Matlab Controlling Toolbox to design the controller. So, it provides an efficient means to improve the dynamic issues on mechatronics equipments and the cybernatic issues on synthetical optimization.