Abstract: In the field of magnetic flux leakage testing, magnetic leakage signal is the basis of test results evaluation. The study of magnetic leakage signal can be divided into forward and inverse directions. The forward problem refers to the study which is from the defect of a certain size to the magnetic leakage signals that defect generate. While the inverse problem refers to making a reverse deducing from the magnetic leakage signals to the shapes of defects, it is so-called inversion. Based on magnetic flux leakage signals of the ferromagnetic floor, the defect recognition, defect location, disfigurement quantitative, and so on were deeply studied. A quantization inversion method based on multiple channels was raised, and the defect test visualization was realized.