Abstract: In order to detect small pitting corrosion defects on the back of the ferromagnetic plate member, a method of pulsed eddy current detection was used to detect and identify the back defects of the test piece. Based on the pulse eddy current testing technology, the pulsed eddy current sensor was designed to test the corrosion defects on three different thickness plates of 3, 6, and 9 mm at the low frequency of excitation frequency of 32, 16, 8, and 4 Hz. Small pitting defects on the surface and back of the plate, The test results shown that circular pitting corrosion defects with a depth of 1 mm and a diameter of 2 mm can be detected, indicating that small pitting defects on the surface and back of the ferromagnetic plate can be effectively detected.