Abstract: The power spectral density peak of the pulsed eddy current testing signal was used as the feature, and the simulation experiment was carried out with the help of COMSOL software, and the relationship between the feature and the pipeline wall thickness and lift-off was analyzed. After that, the research on the wall thickness inversion method based on this feature was carried out, and a method that can be applied to the wall thickness detection of ferromagnetic pipelines under large lift was formed. Finally, experimental tests were carried out on the Q235 pipeline ladder specimen processed in the laboratory. The experimental results show that under the condition of large lift, the wall thickness detection error can be controlled within ±9%, the anti-interference ability is strong, and the multiple measurement results are stable.