Surfactant is a cosmetic material that can reduce the surface tension of water and has many functions. It has the functions of decontamination, wetting, dispersion, foaming, emulsification and thickening, so it is known as industrial MSG. In cosmetics, surfactants are often used as "emulsifiers" to form stable emulsifiers of oil and wax with water. Its chemical structure is hydrophobic at one end and hydrophilic at the other end, which makes it produce significant changes in the interface. According to the source, surfactants can be divided into natural and synthetic two categories, of which commonly used are potassium stearate, sodium lauryl sulfate, Span series and Tween series.