Abstract: Based on the information of sedimentary structure, fossils and metamorphic-deformation, the authors hold that the Shaohuotonggou Formation in the lower part of Hanmushan Group, which has high-grade metamorphic conglomerate, fine-grained clastic rock and carbonate assemblages, was formed in Sinian. Whereas the Caodaban Formation in the upper Hanmushan Group, which is characterized by clastic rock and carbonate assemblage of relatively low-grade metamorphism, was formed in Cambrian. The Caodaban Formation is comparable with the Lower and Middle Cambrian strata in the western margin of Ordos basin.