Understanding the spatial differentiation of soil aggregate stability in mountainous areas is of great significance for assessing the function of mountain ecosystems and preventing soil erosion. In order to explore the spatial variation characteristics and influencing factors of soil aggregate stability in arid mountainous areas, surface (0-10 cm) and subsurface (10-20 cm) soils with different slope orientation (northwest, southeast, northeast and southwest) and elevation gradients (1300-2800 m) in Helan Mountain were selected as research objects. The composition of macroaggregate and microaggregate of soil water stability was determined, and the spatial differentiation of soil aggregate stability was analyzed. The relationships between soil aggregate stability and topography, vegetation and soil properties were revealed. The results showed that the soils in the study area were mainly composed of aggregates with grain size > 2 mm and 0.25-0.05 mm. According to the analysis of Clay Dispersion Coefficient (CDC) and Clay Dispersion Rate (CDR), the stability of soil microaggregates on the northeast slope and southwest slope was better than that on the northwest slope and southeast slope. For the stability index of large aggregates of soil water stability, the Mean Weight Diameter (MWD) and Geometric Mean Diameter (GMD) of aggregates on the northeast slope were the lowest, which were 1.56 mm and 0.44 mm, respectively. The stability of soil water-stable aggregates was the worst. The CDC and CDR decreased, DOA (Degree of Aggregation) increased, and GMD of surface soil increased, while MWD and GMD of subsurface soil decreased with elevation. Redundancy analysis showed that soil physical and chemical properties were the main factors affecting the stability of soil aggregates at different elevations and downslope, in which soil bulk density, capillary porosity, clay content and exchangeability Mg²⁺ were the main factors.