Abstract Nuclear power plant (NPP) is the final goal of the research and developments on the controlled nuclear fusion technologies. Small-diameter tubes, such as the mono-block tubes in divertors, are widely used in Tokamak fusion reactors and other NPPs. To ensure safety of controlled fusion reactors, pre-service and in-service non-destructive testing (NDT) for small-diameter tubes are of great importance. In view of this background, this paper proposes a new array eddy current testing (ECT) probe of high efficiency and detectability aiming for NDT of the small-diameter tubes. The excitation unit of the probe contains large coils of spiral configuration, and the pick-up unit consists of four small pancake coils with rectangle arrangement. The detection signal is taken as the specific difference of the outputs of the pick-up coils. The unique coil arrangement and signal mode can significantly reduce the wobbling noise due to both the probe lift-off change and inclination. The validity and efficiency of the probe configuration are verified in this paper through numerical simulation and experiments. A hybrid FEM-BEM code of A-φ formulation is adopted in the ECT signal simulation, and experiments are conducted by using simplified probe for plate specimen and an array ECT instrument. Both the simulation and experimental results reveal that the configuration of new array ECT probe is capable to detect both axial and circumferential crack in either inside or outside surface of a small-diameter tube.