Abstract: For the problem of defect recognition of magnetic flux leakage pipeline, a method based on threshold analysis is introduced to process MFL defect data. To facilitate image recognition, a series of visual magnetic flux leakage curve is generated. By the use of Delphi programming software, one vertical line can be drawn to locate the girth weld automatically in girth weld recognition and one slash in the form of dots can be drawn to locate the spiral weld in spiral weld recognition which makes the function of automatic weld recognition basically. Also triangle can be used to mark the position of defect. By much identification of different MFL defect, the discrimination of this method in weld and defect recognition is relatively high.