It is difficult to establish a finite element model for a PCB owing to the complexity of the internal structure of the substrate, the large variety of components, and irregular distribution. To solve these issues, this article proposes the distribution and structural characteristics of the components on the main processing board of a vehicle thermal imaging camera as an equivalent modeling method of PCB board dynamic performance based on free modal test data. This method uses the original geometric size of the substrate and the components are processed in different ways according to their physical properties and distribution characteristics on the substrate. Finally, the quality of the equivalent model must be kept equal to the actual model, and the free mode is used. The experimental data and least square method were used to deduce the equivalent stiffness of the substrate and the calculation of Poisson's ratio, respectively. The response curve of the main processing board was obtained through a sine frequency sweep test. The damping ratio corresponding to the first two-order responses was calculated using the half-power bandwidth method, and the damping ratio finite element analysis software was used to obtain the response curve of the equivalent model numerical calculation. A comparison of the response curves shows that the equivalent modeling method meets the actual engineering requirements and provides a reference for the equivalent modeling of similar products.