Giant Bayan Obo Nb-REE-Fe deposit has long been considered typical REE deposit due to its variety of mineral assemblages, complicated geological structure and multiple mineralizations, and an ideal laboratory for study of REE deposits. Its formation mechanism has been on dispute despite 60 years of production and research. This study analyzed and compared the different evidence for the ore-bearing rocks such as dolomitite, K-rich slate, Na-rich and carbonatite dykes by collecting and studying the recently published data. Based on the author's own study, one set of alkaline carbonatite-hydrothermal sedimentary rock was proposed for the mechanism of the ore-bearing rocks in the Bayan Obo deposit. This provides to some extent a reference value for research of the Bayan Obo REE deposit.