Abstract: The paper comprehensively studies the sedimentary environment, tectonic setting, provenance, and their relationship with uranium mineralization in the uranium-bearing strata of Yaojia Formation and Sifangtai Formation in the western slope of Songliao Basin, and analyzes the major, trace, and rare earth elements (REEs) in 30 samples from six representative boreholes. The results show that the ore-hosting clastic rocks are predominantly feldspar lithic sandstone, characterized by various SiO₂ contents, rich alkali, and high contents of Al, Mg and Ca, with low ΣREE (70.08×10^-6-211.33×10^-6), LREE fractionation factor(La/Sm)_N of 2.32-3.96, HREE fractionation factor(Gd/Yb)_N of 1.54-3.25, and moderately negative Eu anomaly. The index of compositional variability (ICV) (0.54-2.30, averagely 0.84) and chemical index of alteration (CIA) values (41.08-68.96, averagely 61.77) of the sandstone reflect moderate chemical weathering in the source area under arid to semi-arid climatic conditions. The discrimination diagrams of source rock indicate that the provenance is dominated by felsic rocks, with minor contributions from ancient sedimentary materials. The discrimination diagrams of major and trace elements suggest that the sandstones of Yaojia and Sifangtai formations are derived from the active continental margin tectonic setting, with provenance primarily from the acidic igneous-sedimentary rock series developed in Daxinganling Mountains.