Abstract: The Yingen-Ejin Banner basin is one of the inland areas in China with low degree of oil and gas geological investigation. A few of previous studies and progress in this area are focused on Mesozoic strata and took them as target stratum for oil-gas exploration. However, basic geological survey during the last decade shows that Permian-Carboniferous strata in this area are very potential for prospecting oil and gas resource. Various characteristics of Permian dark mudstone, such as distribution, abundance, type and maturity of organic matter, mineral composition, reservoir property, shale oil and gas indication, have been revealed by the comprehensive research works based on a large number of core samples from geological survey wells and coalfield drilling in Xirehada area, Yingen-Ejin Banner basin. The result shows that:Permian strata in Xirehada area has wide distribution, large thickness, high abundance of organic matter, high quality source rock of type Ⅱ₁-Ⅱ₂, which has good hydrocarbon generating potential. In these strata, the dark mudstone is rich in brittle minerals and is dominated by illite, with high montmorillonite content, suggesting that it is conducive to the accumulation of adsorbed gas and the formation of fractured fracture. Furthermore, well-developed pore structure in dark mudstone, such as fractures, holes, residual primary pores, secondary dissolution pores and micro fractures, provide good reservoir conditions and indicate good physical properties. Besides, good hydrocarbon shown in core samples further denote that Permian strata in Xieehada area has good prospects for shale oil and gas resources and is a new layer and new field worth to explore.