This dissertation concentrates on the difficult problems that the pipeline or pipe defects are not estimated or evaluated quantitatively, intelligently by MFL (Magnetic Flux Leakage) inspection method. From the practical demand, theoretical analysis and experiments or testing, the MFL inspection technology of pipeline or pipe defects are explained, summarized in detail in the whole paper, at the same time, the relationship between the MFL field distribution, the MFL signal shape and the defect ge...