In order to clarify the magnetic characteristics of a four-redundancy linear force motor for a direct-drive servo valve,the magnetic circuit model of the linear force motor was established by analytical method,and its magnetic circuit distribution,armature stress and armature displacement-force characteristics under normal/fault conditions were analyzed based on Maxwell.The comparison of armature displacement-force characteristics under normal/fault conditions show that the two structures have the same static characteristics under normal operation; in fault mode,the influence of each coil fault on the static characteristics of the force motor is the same under radial layout structure,the influence of each coil fault on the static characteristics of the force motor is related to the position of the faulty coil under axial layout structure.In addition,the frequency characteristics under transient field and the induced electromotive force between coils were analyzed.The results show that the amplitude-frequency characteristics of the axial layout structure are higher than those of the radial layout structure.The magnetic characteristics of four-redundancy linear force motor are analyzed in detail,which provides guidance for its further design improvement.