Abstract: In view of the near surface defects detection, steel plates containing artificial cracks were covered with the sheet metal to simulate the near-surface defects, and the experiment platform of ACFM was built to extract magnetic field signal of the near-surface defects. Experimental data were analyzed, and the optimal excitation frequency, the maximum burial depth and related influencing factors of ACFM on near-surface cracks were obtained, which could provide a reference for the practical detection on the near-surface cracks.