Abstract: The design and development of eddy current transducer were introduced, the relationship between the flaws and characteristics of eddy current signals was analyzed and studied in contact cover, the features of the impedance diagram for the flaws such as cracks were analyzed by comparison. The advantages of the technique by which the flaws were discriminated on the basis of impedance diagram and phase analysis were testified. Through practical testing, it showed that the eddy current testing could increase the testing speed, improved the sensitivity and test accurately.