Rare earth elements (Y, Sc, La-Lu), the "vitamins" of modern industry, are regarded as critical strategic resources in today's society. The Bayan Obo REE-Nb-Fe deposit located in Inner Mongolia, China, is the world's largest rare earth deposit. The diagenesis and mineralization processes of this deposit have attracted a great deal of attention from geologists around the world, and a considerable amount of research has been conducted. These researches were mainly focused on the whole-rock chronology and geochemistry of H8 ore-bearing dolomite rock, which, however, led to confusions over different metallogenic models as the deposit has rather complex ore texture and structure due to late stage deformation and metamorphism. In recent years, with the rapid technological development in modern geochemical analysis, high-precision in-situ isotopic analysis and in-situ U-Th-Pb dating can be performed directly on dolomite and rare earth minerals (such as monazite, apatite, bastnasite, etc.), which yielded valuable information on the age of the deposit as well as the source of ore-forming fluids. This paper summarizes the latest research results on the diagenesis and metallogenic model of the world class Bayan Obo REE-Nb-Fe deposit, and proposes that Mesoproterozoic (1.3 Ga) carbonatitic magmatism initiated REE mineralization and Early Paleozoic metasomatism subsequently caused REE reenrichment and reprecipitation which resulted in the accumulation of large amounts of REE minerals to form the Bayan Obo deposit. © 2022, Editorial Office of Earth Science Frontiers. All right reserved.