Soil aggregation plays a vital role in stabilizing soil organic carbon (SOC), with SOC dynamics within aggregates closely linked to sequestration. These processes are shaped by land use through variations in inputs, microbial activity, and decomposition. We assessed SOC, particulate organic carbon (POC), and mineral-associated organic carbon (MAOC) across aggregate-size classes under five land-use types in the He Huang Valley, Tibetan Plateau: natural grassland (NGL), terrace land (TL), facility land (FL), irrigated farmland (IFL), and abandoned land (AL). SOC content varied significantly by land use and depth, with the highest levels observed in NGL and FL (16.33 g kg- 1 and 15.50 g kg- 1, respectively) at surface depths, and marked depletion under TL and AL. MAOC dominated SOC across most aggregates, particularly in finer fractions, while POC was mainly concentrated in large macroaggregates under NGL (10.83 g kg- 1). POC decreased with depth, whereas MAOC remained relatively stable. Greater MAOC accumulation in FL and IFL microaggregates suggests enhanced mineral stabilization under intensive use. Conversely, TL showed the lowest POC/MAOC ratios, reflecting reduced sequestration potential. Aggregate-associated SOC was strongly correlated with aggregate stability parameters and soil nutrients. Our findings highlight that land use significantly alters aggregate structure and SOC fractionation, with NGL and FL showing the highest potential for carbon stabilization in semi-arid ecosystems.