Abstract: A new eddy current testing method based on preventive multi-filter technology was introduced to test small diameter wire. The different between preventive multi-filter eddy current testing and conventional eddy current testing based on the theory was compered. And through the experimental method, the circumferential sensitivity, blind areas, detection sensitivity of the preventive multi-filter eddy current testing of wire were obtained. The verifying experiment indicated that a vertical flaw of width 30 μm and depth 0.225 mm can be detected.