Wind erosion prevention service (WEPS) is critical for mitigating soil erosion and desertification in China’s arid–semiarid zones. However, most existing studies have overlooked the spatial flow of WEPS, particularly the interannual variability and seasonal dynamics of sand transport pathways. This study focused on the loess hilly–gully region (LHGR), a climate-sensitive zone with intensified aeolian activity. We quantified the spatiotemporal dynamics of WEPS from 2000 to 2020 and simulated sand transport trajectories to assess cross-regional effects and socioeconomic dynamics. The results showed a marked increase in WEPS, indicating improved capacity of wind erosion prevention, with persistently high-value zones concentrated in northwestern arid regions such as the Mu Us Sandy Land. Wind trajectory identified 2,783 transport paths, dominated by spring winds (57.96%), which carried dust eastward toward densely populated areas and transboundary regions like Japan. Beneficiary areas exhibited a concentric spatial pattern, covering 599.96 × 10 4 km² (62.5% of China). The growing population, gross domestic product, and ecosystem service value highlighted its dual role in safeguarding human health and supporting sustainable development. Fraction vegetation coverage (FVC) emerged as the dominant factor for actual wind erosion by increasing surface roughness, with China’s ecological restoration policies amplifying this function. Precipitation (PRE) predominantly regulated potential wind erosion, while synergistic interactions between FVC, PRE, and other drivers underscored the necessity for multi-factor governance. Our framework integrating physical flow and beneficiary mapping provides practical insights for optimizing payment for ecosystem service to enhance cross-regional ecological benefits.