Anionic emulsifiers are a class of emulsifying agents whose hydrophilic groups acquire a negative charge upon dissociation in aqueous solution. Their molecular structure consists of hydrophobic carbon chains and negatively charged hydrophilic groups, primarily including sulfonate, sulfate, carboxylate, and phosphate groups. These emulsifiers function by orienting at oil-water interfaces and generating strong electrostatic repulsion to prevent droplet coalescence, thereby forming stable emulsion systems. Compared to conventional surfactants, they demonstrate enhanced emulsifying capacity and superior dispersion stability. Representative products include sodium stearoyl lactylate, diacetyl tartaric acid esters of monoglycerides, and sodium alkyl sulfates, widely used in food industry (e.g., bread, cakes, margarine), cosmetics (e.g., creams, lotions), and pharmaceutical sectors. They perform optimally in acidic to neutral environments, though their effectiveness may be compromised in strongly acidic conditions or hard water, with additional considerations needed for compatibility with cationic substances.