Abstract: Magnetic flux leakage(MFL) testing is widely used to inspect and characterize defects in pipelines, storage tanks and other structures. In this paper, based on the Maxwell Equations, numerical simulation and experimental research of crack magnetic flux leakage field were carried out. The threedimensional models of cracks were established, the influence of the generalized crack parameters to the magnetostatic MFL field, including depth, width, inclination angle and crack spacing, was discussed. The relationship between defect parameters and MFL amplitude was obtained. The amplitude was significantly affected by the inclination angle. Therefore, single direction inspection could lead to undetected in practice. While the two cracks interval was less than 5 mm, the MFL fields would overlap. Furthermore, the experimental investigations were developed, and the results agreed well with that of the simulation. The conclusions could provide valuable reference for inspection.