The Chang 7₃ sub-member of the Yanchang Formation in Ordos Basin represents an important layer of uranium-rich source rocks. Exploring the genesis of phosphorus-bearing minerals and the mechanism of uranium enrichment are of great significance for deciphering basin evolution and uranium mineralization. The geochronology of phosphorus-bearing minerals and uranium enrichment mechanisms is investigated by using electron microscopy, laser ablation inductively coupled plasma mass spectrometry, U-Pb geochronology, and geochemical analysis. Results indicate the following: (1) The formation of phosphorus-bearing minerals can be divided into two independent stages. During the early sedimentary-diagenetic stage, influenced primarily by volcanic activity, volcanic ash tends to serve as the main source of both phosphorus and uranium. The coupling of high primary productivity and organic matter decomposition synergistically contributes to promoting apatite precipitation. During the Late Cretaceous hydrothermal diagenesis stage, the U-Pb isotopic systems of apatite were reset, yielding ages of 84 ± 2 Ma and 68 ± 1 Ma. This event also significantly modified the REE distribution patterns, resulting in flattened chondrite-normalized patterns and obvious LREE depletion. (2) Uranium enrichment in phosphorus-bearing minerals, which is closely associated with their formation, occurred through a two-stage process. During the sedimentary stage, U⁶⁺ was reduced to U⁴⁺ and incorporated into the mineral lattice via isomorphous substitution for Ca²⁺ or adsorbed onto mineral surfaces through complexation. Whereas the subsequent hydrothermal diagenesis stage led to further uranium enrichment as hydrothermal fluids introduced additional U⁶⁺, which was reduced to U⁴⁺ under anoxic conditions and incorporated into the apatite lattice via isomorphous substitution for Ca²⁺ or precipitated as discrete uranium minerals.