Demulsifying agent as well as preparation method and application thereof

The invention relates to a demulsifying agent as well as a preparation method and an application of the demulsifying agent. The preparation method comprises the steps: (1) in the presence of an interesterification catalyst and a polymerization inhibitor, carrying out interesterification on a polyether raw material and methyl ester of unsaturated carboxylic acid and/or ethyl ester of unsaturated carboxylic acid; (2) separating methanol and/or ethanol by virtue of reduced pressure distillation; and (3) mixing with the unsaturated carboxylic acid, 2-acrylamide-2-sodium methallyl sulfonate, water and a free radical polymerization initiating agent to perform free radical polymerization. The demulsifying agent prepared by using the method is particularly suitable for demulsification and dehydration of high asphaltene thickened oil.