The effects of different pH values (3, 5, 7, and 9) on the stability, physicochemical properties, and antioxidant capacity of Astragalus polysaccharide and soybean oil body (APS-SOB) composite emulsions during 28-day storage were investigated. Composite emulsions were prepared from soybean and APS and characterized through indicators such as particle size distribution, zeta potential, and emulsion stability. pH significantly influenced the emulsifying performance and stability of APS composite emulsions. At pH 9, the composite emulsion had the smallest particle size (804.29 nm), and no significant phase separation was observed after 14 days of storage. When the storage period was extended to 28 days, the composite emulsion maintained the lowest levels of hydroperoxides (8.83 mmol•kg-1), Tbars (4.99 μmol•kg-1), and acid value (3.90 mg•g-1) at pH 9, concluding that alkaline conditions were more favorable for APS-SOB composite emulsion stability, providing theoretical support and technical parameters for developing high-stability, antioxidant functional emulsion-based foods.