The mafic-ultramafic intrusions contain a large amount of information from the deep earth, and the magmatic deposits they contain are of great economic value. Fe is an element directly involved in mineralization, and Fe isotope method has a natural advantage in tracing the source of metallogenic material and metallogenic process. In recent years, with the appearance and development of MC-ICP-MS, many scholars have carried out a series of Fe isotope studies on mafic-ultramafic intrusions and made important progress. In this paper, the fractionation mechanism of Fe isotopes in mafic-ultramafic intrusions is discussed by summarizing the composition characteristics of Fe isotopes in magmatism and metallogenesis. The results show that the composition of Fe isotope in different geological bodies is different. The chondrite represents the initial Fe isotope composition of the earth, and the other geological bodies are subjected to different degrees of later geological processes and produce fractionation of Fe isotope. The framework of Fe isotope fractionation mechanism in mafic-ultramafic intrusions is constructed: Fe isotope fractionation mechanism includes thermodynamic equilibrium fractionation and kinetic fractionation. In natural minerals, Fe³⁺ forms stronger chemical bonds than Fe²⁺, so mineral rich in Fe³⁺ (such as magnetite) are more enriched in heavy isotopes than mineral rich in Fe²⁺ (such as pyrrhotite and pentlandite). Many kinetic processes such as redox process, fractional crystallization, partial melting and diffusion are the factors leading to kinetic fractionation. Due to its unique geochemical properties, Fe isotopes have a wide application and prospect in the fields of Cu-Ni-PGE sulfide deposits, V-Ti magnetite deposits and chromite deposits related to mafic-ultramafic intrusions. Combined with other stable isotopes, such as Li-S-Mg-Ni isotopes, they can be used to trace the assimilation of sediment, invert the crystallization process of sulfide melt and reveal the genesis of deposit.