Abstract: The magnetic flux leakage (MFL) method is widely used in-line inspection technique for the evaluation of gas and oil pipelines. The actual status of the defects in the pipeline is very complex. It is very difficult to research the changing rule of magnetic flux leakage field by using physics experiment method. In this paper, the MFL signals obtained during the inspection of steel pipelines has been simulated using 3D finite element analysis. The interaction of the adjacent defects has been studied. The numerical simulations imply that the adjacent defects have significant effects on the character of the MFL signals. The results show that the effect is minimal with the parallel alignment defect, and the effect is maximal with the group defect.