Abstract: Because it is still difficult to find an efficient theory and method systemically in the solutions to electromagnetic fields and its inverse problems, the signal quantitative interpretation methods have been the key to magnetic flux leakage testing technique all the time. Based on the review of current research and development for MFL signal interpretation methods, the difficulty of defect quantitative characterization via MFL testing signals was analyzed, and the capabilities and limitations of the model matching method and the statistical relation model were presented. The advantages and disadvantages of the artificial neural network were mainly discussed. And such research tendencies of the MFL signals interpretation as visualization, multi-sensors data fusion were pointed out.