Abstract: The age assignment of the Bayan Obo Group has long been disputed mainly for lack of reliable paleontological evidence. The author and his colleagues found large amounts of Early Cambrian small shelly fossils in the original Archean and Proterozoic strata within the realm of the "Inner Mongolian axis"on the northern margin of the North China platform. On the basis of the appearance of small shelly fossils and recognition and discussion of strotomalites and isotopic ages, the author expounds his view and augurnents. He holds that the Bayan Obo Group, Zhartai Group and Huade Group were all formed in the early Early Paleozoic and are the contemporaneous products. They can be correlated.