Bacterial magnetosome, synthetized by magnetosome-producing microorganisms including magnetotactic bacteria (MTB) and some non-magnetotactic bacteria (Non-MTB), is a new type of material comprising magnetic nanocrystals surrounded by a phospholipid bilayer. Because of the special properties such as single magnetic domain, excellent biocompatibility and surface modification, bacterial magnetosome has become an increasingly attractive for researchers in biology, medicine, paleomagnetism, geology and environmental science. This review briefly describes the general feature of magnetosome-producing microorganisms. This article also highlights recent advances in the understanding of the biochemical and magnetic characteristics of bacterial magnetosome, as well as the magnetosome formation mechanism including iron ions uptake, magnetosome membrane formation, biomineralization and magnetosome chain assembly. Finally, this review presents the potential applications of bacterial magnetosome in biomedicine, wastewater treatment, and the significance of mineralization of magnetosome in biology and geology.