Abstract: The fast switching device has high du/dt and di/dt, which makes itself become an interference source and produces electromagnetic interference to the surrounding equipments. In this paper, the interference source above the magnetic latching relay is simulated by magnetic steel, and the static interference model is established by finite element analysis software. The influence of the external magnetic steel at different positions on the torque of the armature has extreme value, and the golden section method is used to solve the space sensitive position of the magnetic latching relay. The results show that the sensitive direction of magnetic interference is parallel to the armature component, and the sensitive position exists in the sensitive direction with maximum magnetic interference. Then, the dangerous area of the magnetic latching relay is worked out.