Halting land degradation and desertification in arid regions through ecological conservation and restoration is a globally important issue. In the Northern Sand Control Belt that traverses China, ecological restoration efforts are still confronted with problems such as secondary land degradation and water resource constraints. The challenges indicate that on a large spatial scale, it is crucial to analyze the process of wind-blown sand movement and establish a systematic protection and restoration system from the source to the end based on ecosystem service flows. We developed a process-based framework synthesizing land use patterns, topographic features, and aeolian dynamics to quantify spatiotemporal disparities in Windbreak and Sand Fixation Service (WSFS) supply-demand relationships, unravel the mechanisms underlying service flow pathways, and delineate conservation and restoration priorities. Employing a novel service flow model parameterized with multi-temporal remote sensing data (2000-2020), we demonstrate two mechanistic findings: (1) Spatiotemporal analysis revealed that 9.66% of the study area functioned as source-dominated zones for wind-sand regulation services. This suggests that past restoration efforts have paid more attention to the source type. (2) Protection priorities hierarchically followed service flow surplus gradients, whereas restoration priorities exhibited sequential transitions aligned with deficit severity. Our findings establish a novel process-mechanism framework that resolves persistent challenges in aeolian sediment management through spatiotemporal optimization of service flow dynamics. These insights carry immediate operational relevance for China's Northern Sand-Prevention Belt where precision interventions prove imperative in reversing desertification trajectories.