Abstract: Regional geology and tectonic characteristics were investigated for Bayan Obo and surrounding areas in northern Inner Mongolia The results place constraints on paleoplate tectonic units, the tectono-sedimentary settings of Bayan Obo Group and the features of tectonic assemblages in this region. The Bayan Obo Group Call be divided into three sedimentary associations which represent the transition processes of sedimentary environments within rift basins from interior continent at Mesoproterozoic to continetal margin at Neoproterozoic，and to active continental margin at Early Paleozoic． There are important differences in geology and tectonics between southern and northern regions along Bayanjiaolake-Kuanggou Fault as a boundary．The rocks in the southern region uncomfomlably overlies the rocks of Seertengshan Formation in Wutai Group and thus the sedimentary rocks of continental margin are developed on the continental basement of North China．Some strata of carbonate and shale underwent intensive metasomatism of mantle-derived fluid at Early Paleozoic，forming a large scale REE mineralization. Regional metamorphism overprinted both metasomatic and unmetasomatic strata again at Late Paleozoic．The Bayan Obo Group in the northern region is characterized by development of ophiolite me1ange，imbricate thrust and tightly synclinal fold，corresponding to accretionary complex scrapped off during plate subduction A preliminary scheme is presented to outline the geodynamic processes of tectonic evolution associated with plate subduction in Bayan Obo Region.