Abstract: In order to solve the problem that the location and degree of defects of oil storage equipment such as oil pipeline with cladding layer are not easy to be determined due to corrosion, a set of defect detection system of ferromagnetic materials based on pulse eddy current is developed and designed according to the advantages of wide spectrum and strong signal penetration ability of pulse eddy current detection. Through the design of a new type of detection sensor, the precise measurement of the defect position is realized. Through the quantitative relationship between the time-domain and frequency-domain eigenvalues of the detection voltage signal and the changes of ferromagnetic materials with different thickness, the defect degree of the test piece is determined. The experimental results show that the system can accurately detect the thickness and defect degree of ferromagnetic materials under 20 mm coating layer, which has a certain application value.