Abstract: Probe is critical component of Eddy Current Array technique, so a new kind of eddy current internal array ECT probe named X-probe is introduced in this thesis。 The X-probe’s operation principle is analyzed. Its defects signal characteristic, signal response in TSP and relationship of defect depth & signal phase are studied through the experiments. Finally, application of X-probe in eddy current testing of NNP condenser heat-exchange tube is introduced. Experiment results show that X-probe can achieve defect profile and distinguish defect direction by AF and CF channel signal voltage. Field application proves that X-probe has good detection ability within TTS zone tube and can well distinguish complex defects and measure defects depth.