Abstract <p>Pengyang uranium deposit in the southwest of Ordos basin is a large-scale uranium deposit which is first discovered in the deep red bed. This study mainly elucidates the characteristics of sedimentary system of uranium-bearing layer and its relationship with uranium mineralization. By means of the field survey, detailed geological record of boreholes, compilation of sedimentary maps, and the experimental analysis of petrology, scanning electron microscope and grain size, the characteristics and evidences of aeolian deposit in the uranium-bearing layer are further determined. Finally, uranium mineralization is discussed from the aspects of sedimentary facies, gray sandstone, uranium minerals. The results show that the sedimentary facies of Luohe Formation of the area are mainly composed of aeolian dune, sand sheet, dry valley deposit, and a small amount of desert lake. The geological record shows that the typical aeolian sedimentary markers include wedge-shaped cross-beddings with high angles, grainflow strata, wind ripple strata, pin stripe and wind erosion gravels. The results of rock and mineral identification reveal that the uranium-bearing sandstone is mainly fine-grained feldspathic lithic quartz sandstone. The cumulative curves of grain size from the core samples show a characteristic of typical two-stage transport. The saltation transport is the major part. And the typical dish-shaped impact features on the surface of quartz are commonly developed in core samples, which is similar to the analytical results of outcrops and modern desert samples. In addition, uranium mineralization mainly occurs in the grainflow strata. Based on the sedimentary facies profile and plan compiled by the borehole data, the favorable positions of uranium mineralization in the region are shown, which provides the basis for the future prospect prediction. Red-yellow-gray color alteration zoning and altered minerals on a microscopic scale reveal that the gray aeolian sandstone in Luohe Formation is controlled by later reductive alteration. The coupling of the uranium-oxygen-bearing fluid and the deep hydrocarbon-bearing fluid is probably the main uranium mineralization in the primary aeolian deposit of Luohe Formation in the southwestern Ordos basin.</p>