Ordos basin is the potential target zone of CO₂ underground storage in China. Well Zhongshenjian X is located near the Ejin Horo Banner, neighboring the underground CO₂ injection well "Zhongshenzhu One", and the two wells have the same formation system and rock composition. To predict the potential of carbon sequestration in the reservoir and the mudstone transformation conditions in the demonstration area and provide basic geological information and relevant data for numerical simulation of the CO₂ geological storage, the authors investigated petrologic and geochemical characteristics of Shiqianfeng Formation in well Zhongshenjian by means of polarizing microscope, SEM, X-ray diffraction and X ray fluorescence, and the results suggest that the sandstone of Shiqianfeng Formation is mainly feldspathic lithic sandstone and lithic feldspar sandstone, and the mudstone is mainly composed of quartz, clay minerals and feldspar, in which the clay minerals are mainly smectite and illite, followed by kaolinite and chlorite. It is inferred that sandstone in Shiqianfeng Formation could form the mineral trap relative to the CO₂ leaks by forming carbon sequestration minerals such as dawsonite, calcite, ankerite and siderite, and then the long-term and safe storage of CO₂ could be realized. In addition, metals were mobilized, resulting in the bleach of the red mudstone interlayer.