For under-surface cracks, the maximum time of the induced magnetic field will appear as the depth of the defect increases; however, for surface cracks, the maximum value of the induced magnetic field at different depth cracks appears almost the same. This shows that the pulsed eddy current is more suitable for the quantitative detection of subsurface deep cracks. In practical applications, the corresponding curves of the depth and the maximum occurrence time of the induced magnetic field can be drawn according to the response data of the artificial defects of different depths. After the time when the maximum value of the defect response signal is detected in the actual detection, it can be corresponding to the reference curve. Determine the depth of the defect.