Abstract: Multilayer printed circuit board (PCB) is always internally installed in the electronic equipment cabinet.External electromagnetic interference is probably pass into the device through the external wire and cause internal damage to the PCB.In order to study the problem, the full wavelet method is adopted to get the corresponding parameters of the interfered device.Then, the equivalent source model is generated by using these parameters.Finally, the electromagnetic properties of the PCB in the device are analyzed by the equivalent circuit method.Full wavelet method combined with the equivalent circuit method analyze the influence of the external electromagnetic on the equipments.The research provides a new method and idea on studying the equipments in high frequency electromagnetic interference environment.