Abstract: Magnetic flux leakage techinique had been widely used for non-intrusively testing of steel products.The principle of pulsed magnetic flux leakage testing(PMFL) was analyzed. A pulsed alternating current magneting method was presented. The finite element numerical simulation had been used to simulate and calculate the effects on various of parameter of the detection system. The influences of changes of lift-off, defect depth and length of the pulsed magnetic field leakage were studied by way of finite element numerical simulation. The results showed that PMFL had the advantage of high signal amplitude and more useful testing information, and this making the method had the broad using foreground in the testing of steel pipe.