An innovative light scattering immunoassay was developed using an AuNPs etching strategy. Three types of anisotropic gold nanoparticles, including gold nanocubes, nanorods, and nanoflowers with distinct morphologies, were utilized to investigate how these morphological differences affect the sensitivity of light scattering signal transduction. Based on theoretical insights into light scattering and electromagnetic fields, gold nanocubes were identified as the optimal probes for enhancing light scattering signal transduction and were employed to construct an immunoassay for detecting staphylococcal enterotoxin A (SEA). The developed immunoassay achieved ultrahigh sensitivity for SEA detection in milk samples, with a detection limit of 10.39 pg mL