Abstract: Finite element simulation was used to analyze the relationship between MFL and the lift-offs, defects width, depth and in-rope depth. It concluded that lift-offs was not the smaller the better; the sum of defects width and lift-offs were equal to the distance of peak-peak at the radial part of MFL; the axial part of MFL and defect depth were in linear relation approximately, so were the defects in-rope depth.