Defect reconstruction method for magnetic flux leakage (MFL) testing is a hot and difficult spot of MFL testing defect evaluation nowadays. Reviewing the contents of the MFL testing defect reconstruction research, two kinds of defect reconstruction methods: open loop reverse method and closed loop pseudo-reverse method have been summarized. And the reverse model, forward model and optimization algorithm which are commonly used in them were discussed here. Furthermore, the research direction of defect reconstruction such as data fusion technology, image processing technology and the comprehensive assessment of multi defects were proposed.