Anionic surfactants are a category of surface-active agents whose hydrophilic groups acquire a negative charge upon dissociation in aqueous solution. Their molecular structure consists of hydrophobic carbon chains and hydrophilic groups, primarily including sulfonate, sulfate, carboxylate, and phosphate groups. These surfactants function by reducing surface tension to produce wetting, emulsifying, dispersing, and foaming effects, with particularly outstanding foaming capacity and detergency. Common anionic surfactants include linear alkylbenzene sulfonates, fatty alcohol ether sulfates, alpha-olefin sulfonates, and soaps. They are widely used in detergents, personal care products, textile dyeing, and pesticide emulsification, though their effectiveness may be compromised in hard water due to insoluble salt formation with calcium/magnesium ions, while biodegradability and ecotoxicity vary depending on specific molecular structures.