Abstract: Based on the magnetic flux leakage(MFL) data of the butt weld of the steel plate, a MFL visualization method of the weld based on pseudo-color is proposed. Firstly, three kinds(weld with no-defect, rectangular slot defects in the heat affected zone, rectangular slot defects in the weld) of MFL signals are collected by the new MFL system(magnetization direction is perpendicular to marching direction), then three-dimensional spatial distribution are generated. And by the gradation linear transformation, it is converted to the two-dimensional grayscale graphics. Afterwards, by the gradation-color conversion method, the generated grayscale image is converted into the pseudo-color image. The test results indicate that the weld defect feature information can be displayed intuitively by the pseudo-color image; the method can enrich details and layering of the MFL image, and enhance the identification ability to the defect feature, with better visual effects.