<p>Sediment grain size characterization is a fundamental component of aeolian sedimentological research, as it constrains the provenance of sedimentary materials, their formative and evolutionary processes, and associated depositional environments. The Ulan Buh Desert is a major source of aeolian dust in northern China and East Asia and is particularly significant because of its substantial contribution to Yellow River sediment. In this study, the grain size characteristics of surface and subsurface sediments from the Ulan Buh Desert were examined based on regional sedimentological records. The results indicated that both sediment layers were dominated by fine and medium sand, with mean grain sizes of 2.25 Φ and 2.34 Φ, respectively. The surface and lower sediments exhibited highly comparable distribution patterns, indicating largely analogous formative mechanisms. Desertification within the Ulan Buh Desert was primarily governed by local aeolian entrainment. A systematic spatial trend of grain size fining from northwest to southeast was observed across the region. Sediment transport was dominated by saltation, which has been identified as the principal mode by which sand can be delivered to the Yellow River, with fine sand serving as the main material involved in this process. Furthermore, late Quaternary sedimentary records from the Ulan Buh Desert demonstrated environmental evolution characterized by alternating lake and desert phases.</p>