The mechanism of crude oil demulsifier is phase transfer-reverse deformation mechanism. After the demulsifier is added, a phase transition occurs, that is, a surfactant (reverse demulsifier) that is opposite to the type of emulsion formed by the emulsifier can be generated. This type of demulsifier reacts with the hydrophobic emulsifier to form a complex, so that the emulsifier loses its emulsifying properties. The mechanism of collision breaking the interface film. Under the condition of heating or stirring, the demulsifier has many opportunities to collide with the interface film of the emulsion, or adsorb on the interface film, or eliminate the substitution of some surface active substances, thereby breaking the interface film and greatly reducing its stability. Flocculation, coalescence and demulsification.