Abstract: Bacterial cells, growing naturally in freshwater and marine environments or experimentally in culture, can precipitate a variety of authigen ic iron minerals. Iron hydroxides and oxides are commonest among them. This pape r introduces several mechanisms of microbial mineralizations of iron, including hydroxides, oxides, magnetite, and silicates etc. According to the relationship between biomineralizations and living things, there are two kinds of biominerali zations: the biologic ally induced mineralization and the biologically controlled mineralization. Bact eria may bind metals on charge surface, and their metabolic waste products in th e surrounding environment may induce mineralizations. From the freshwater to the marine environments, from the ancient to the modern geochemical cycles, bacteria get involved in iron circulation from the microcycles to the world scale. The u b iquitous presence of bacteria in aquatic systems and their inherent ability to b iomineralizations, therefore, makes them important agents in driving both modern and ancient geochemical cycles. In addition, the study of biomineralizations can be applied to a variety of fields, including civil engineering, nano-materials and environment protection.