Abstract: In order to overcome the shortcomings such as missing detection or long time consuming in the detection of the circumferential defects of the small-diameter tube by traditional probes, an eddy current probe for such defects was designed. The finite element simulation and experimental methods were used to optimize the geometric parameters of the probe. The influences of thickness, width of the magnetic material, diameter of the excitation coil, and number of turns on the detection of the circumferential defect of the small diameter tube were analyzed, which provided references for optimizing the detection performance of the probe. Compared the detection of standard flaws between the new type of probe and a conventional eddy current probe, it was found that the detection of circumferential defects by the former one is more powerful than that by the latter.