In the present paper, different kinds of high permeable alloys invented both in abroad and home were described, and a theory of high permeability was put forwards. Alloys of constant permeability was also described. Lastly a description regarding alloys used as permanent magnets, such as K. S. magnet steel, M. K. magnet alloy, Kato's sintered magnetic alloy and New K. S. magnet alloy, was given together with the theory of high coercive force. As a support of this theory, an interesting fact was observed that pure iron which was specially treated, showed a high coercive force as high as 150 Oersteds.
