Compared to the sandstone-type uranium deposits in the Ordos Basin and the Songliao Basin, the Tamusu uranium deposit in the Bayingobi Basin formed in fault-depression transition region displays distinctive features. First, the uranium-bearing sandstones and their interlayer oxidation zone extend longitudinally no more than ten kilometers. Second, gravity flow sediments are more common in the uranium-bearing strata. Comprehensive facies analysis indicates that the Upper Member (ore-bearing horizon) of the Bayingobi Formation was largely deposited in fan deltas that prograded into lakes during period of relatively dry paleoclimate. Spatial distribution patterns of five facies associa-tions along with two depositional environments (fan delta, lake) were reconstructed in this study. The results demonstrated that the depositional systems and their inner genetic facies played different roles in uranium reservoir sandstone, confining beds (isolated barrier beds) and reduction geologic bodies during uranium mineralization process.