Abstract: Magnetic flux leakage(MFL) testing technology has been applied to test of the in-service cable with the development of bridge inspection. Due to the complexity of structural characteristic of cables, MFL testing on cable is characterized by the major diameter and liftoff, which make the background magnetic field higher. A MFL testing model is established using the 3D finite element simulation method. The authentic signals of magnetic leakage field are obtained by subtracting the magnetic field signal of no defect from the defective field signals. The relationships of distribution of the MFL field are achieved, which are influenced by many parameters, such as broken wire’s width and burial depth, etc. And then, the curves are obtained representing distribution of the MFL field to above parameters. Finite element simulation provides the basis for interpretation of MFL testing results and plays an important role in quantitative analysis of broken wires.