Abstract: Quantification for width, depth and volume of defects on pipeline with insulation is a difficult problem. A method of using pulsed magnetic flux leakage technique on testing corrosion defects on pipeline was proposed. Different features in time-domain were extracted to analyze the variation of the features and parameters of the defects, then the quantification for width, depth and volume of the defects could be realized through the obtained formula of the variation. The validity of the new method was demonstrated by experimental results.