Eddy Current Test (ECT) is proven to be the most reliable non-destructive assessment for electrically conductive materials. This assessment works based on the emerging Eddy Current when an alternating current is induced into conductive materials. The ECT system consists of three elements, i.e. current injection, the pick-up, and the conductive target. This system is then treated as an altered wireless power network between aforementioned elements. The use of alternating current (A/C) in this network provides a wide variety of power spectra for various analysis techniques. This paper introduces novel technique of subsurface crack assessment on SMAW welded joint of stainless steel 316 L by applying network altered response to ECT system. The analysis of the network is done by constructing mathematical models of the frequency domain in each component in the network to achieve the gain of the system. The mathematical model was constructed either for the defectless and the defected speciments, and then both result was compared to investigate and extract the information about the crack. The experiment also performed to confirm the simulation from the modeling. The experiment succeeded to differentiate the size of the subsurface crack on certain working frequencies.