Abstract: The Carboniferous is well developed in the Ju Ud League area, Nei Monggol. The author suggests that the Carboniferous may be divided into the northern and southern lithofacies zones with the Wudan-Naiman Caledenian uplift as the boundary. He has systematically summarized the basic characteristics of the strata of the two lithofacies zones and made a new division of the lower Carboniferous. The Tournaisian deposits have been established below the Baijiadian Formation and named the Xiamaquanzi Formation. The Chaotugou Formation that was assigned to the Tournaisian stage by predecessors has been assigned to the middle and upper series of the Devonian. The middle Carboniferous Huangjiagou Formation of continental origin has been determined according to previous data. The author has also collected and analysed paleontological data, summariaed and classified Carboniferous biotas, and made a simple correlation with strata at home and abroad from a biostratigraphic view of point. Through summing up the stratigraphic and paleontological data in the area and analysing and discussing the Carboniferous lithofacies and paleogeography, the author suggests the significance in coal formation for the area where the Jiujuzi, Huangjiagou and Baijiadian formations are deposited.