Abstract: Aiming to reduce the large error between the assumed uniform magnetic charge distribution in the analysis of leakage magnetic field and the actual engineering results, the non-uniform distribution law of magnetic charge after magnetization of pipeline defects was studied, and the distribution characteristics of magnetic charge on the side wall and edges of pipeline defects were obtained. Based on the magnetic dipole theory, the three-dimensional magnetic dipole analytical model of pipeline defect was established, the leakage magnetic field generated by the edge magnetic charge of the defect and the magnetic charge of the non-uniform surface of the side wall was solved, and the experimental research was carried out. The calculation results and the actual defect leakage magnetic field distribution characteristics of pipeline were in very good consistency, and the actual error of the leakage magnetic field was smaller than that while the distribution of magnetic charge being assumed uniform. It is shown that the model can effectively describe the distribution characteristics of leakage magnetic field with rectangular defects.