Abstract: To elucidate the mechanisms by which the amount of vinegar added affects the preparation and rheological properties of plant-based mayonnaise made from soy protein. This study investigates the effect of varying vinegar addition amounts on the formation, microstructure, and rheological properties of SP-based emulsion gels for plant-based mayonnaise. Using analytical techniques such as static and dynamic light scattering, confocal laser scanning microscopy, and shear rheology, this work aims to optimize the formulation of SP-based vegan mayonnaise. The results demonstrated that vinegar-induced pH adjustments (3.72–6.34) alter the conformational stability and charge distribution of SP, subsequently influencing emulsion droplet characteristics, microstructural organization, and viscoelastic behavior. At low vinegar addition amounts (<5.0%), emulsion droplet size and polydispersity index increased significantly, accompanied by a shift in zeta potential from -27.17 mV to 2.45 mV. Conversely, moderate acidification (7.5%–10.0% vinegar) enhanced protein emulsifying capacity, yielding smaller, monodisperse droplets with an elevated surface charge (9.29 mV). All emulsions exhibited shear-thinning behavior; however, the apparent viscosity peaked at a 5.0% vinegar addition amounts, while the elastic modulus (G') peakd at 2.5%. A subsequent 35% reduction in G' was observed as acidification intensified to 10.0%, indicating compromised gel network integrity under excessive protonation. Correlation analysis revealed a non-linear relationship between G' and droplet size, whereas a strong inverse correlation existed between G' and the absolute value of surface charge. This suggests that vinegar-mediated modulation of gel strength arises primarily from electrostatic interactions between droplets rather than particle packing effects. These findings elucidate the pH-dependent structure-function relationships governing soy protein emulsion gels, providing a theoretical framework and technological strategy for developing plant-based spreads with tailored textural properties.