Abstract: Eddy current testing is the preferred method of corrosion inspection to the inner layer of the multi-layer metal structure. To solve the problem of testing, the aircraft skin sandwich structure corrosion flaw, the low-frequency eddy current testing method was established. The optimum frequency was selected considering about the single magnitude and the phase separation of the depths corrosion flaw. The aircraft skin sandwich structure corrosion flaw was identified, using as-prepared eddy current probe and utilizing the difference of phase and magnitude. This would give a reliable testing method for aircraft reconstruction.