Abstract: Based on the theory of magnetic flux leakage testing, the theoretical calculation formula of finite element dynamic analysis of magnetic flux leakage testing is studied, and the finite element dynamic simulation model is established. From the perspective of finite element analysis and experimental research, the magnetic flux leakage distribution characteristics of pipeline defects and patch are studied. In the finite element analysis model, the distribution of leakage magnetic field of defect and pipeline patch is studied from the radial and axial direction of pipeline, and the distribution curve of leakage magnetic field is drawn. An internal magnetic flux leakage test platform was built, and the radial distribution characteristics of the magnetic flux leakage of the defects and the patch were studied by using different sizes of artificial defects and patches. The simulation analysis and test results show that although it is casy to cause confusion because the distribution law of magnetic flux leakage field of pipeline patch is similar to that of defect in the process of magnetic flux leakage testing, the magnetic flux leakage signal generated by defect and patch can be determined by the sequence of positive and negative peaks.