Abstract: The research of arithmetic on the basis of emulation mode in Ansys aimed to eliminate the support signal and extract the defect signal. According to the theory of impedance analysis, it simulated dual-frequency eddy current testing by the differential sensor and gets impedance data. On the basis of these data phase rotation and subtraction mixing method were applied and the extraction of the defect signal from a combination of the support signal was realized. The analysis indicated that this method was universal and was effective to distinguish between the defect signal and the support signal.