Abstract: In this paper, a concentric square coil profiling eddy current sensor is designed for a specific aero-engine turbine blade tongue and groove. Under different excitation modes and excitation frequencies, electromagnetic simulation tests are carried out on the engine blade tongue and groove. The simulation results show that under the excitation frequency of 500 kHz and the excitation mode of external coil, the concentric square coil sensor can detect four longitudinal defects with length of 1. 0 mm, width of 0. 2 mm or 0. 1 mm, depth of 0. 5 mm or 1. 0 mm, and three circular defects with radius of 0. 1 mm, depth of 0. 5 mm or 1. 0 mm, radius of 0. 05 mm and depth of 1. 0 mm. It was also found that the circular defects of radius of 0. 05 mm with depth of 0. 5 mm could not be detected.