Alloys are used in a variety of structures and functional materials because of their excellent functional and mechanical properties. In particular, since alloys exhibit various characteristics depending on the composition of elements, the utilization of the alloy may be improved by adjusting properties according to specific applications. However, designing various combinations under experimental conditions has the disadvantage of taking time and cost, so it is limited to designing alloys that meet specific conditions. Therefore, in this thesis, a computer simulation method for improving the properties of alloys was studied. In detail, Fe alloys were modeled by computational simulation to improve the mechanical and functional properties. We analyzed the effect of each element constituting the alloy on the properties of the alloy, and improved its properties through alloy design method. Chapter1 is a study on nitriding, one of the methods to improve the mechanical properties of Fe alloys. The nitriding treatment is environmentally friendly, economical, and can treat the surface of a reinforced Fe alloy of excellent quality, but it takes a long time. Therefore, the design of alloys for enhancing the nitriding rate was studied. In Chapter2, computational simulation studies have been described to improve the magnetic property of high entropy alloys (HEAs), which have recently become widespread issue in the military and society.