The invention provides a method for preparing a condensed oil-water emulsion emulsion-breaking agent by taking phenol as a raw material. The method comprises the following steps: adding the phenol into a reaction tank; raising the temperature and stirring; adding a catalyst and 1500# solvent oil; cooling and dropwise adding formaldehyde; raising the temperature, reflowing and distributing water toobtain phenolic resin; cooling the phenolic resin and vacuumizing the reaction tank; adding a potassium methoxide solution, stirring, vacuumizing and raising the temperature; inflating nitrogen gas to normal pressure; dropwise adding propylene oxide for a plurality of times; keeping temperature and pressure; vacuumizing and cooling; after dropwise adding fumaric acid, inflating the nitrogen gas and raising the temperature to obtain an esterified object; adding the esterified object into a reaction kettle; vacuumizing and raising the temperature; adding p-toluene sulfonic acid and stirring; adding monoethanolamine and stirring; adding methanol and stirring to obtain an emulsion-breaking agent. The method provided by the invention has the advantages that the stubborn emulsified liquid problem in a natural gas well mining field is solved through a prepared emulsifier; the oil content of sewage treated by natural gas mining liquid is greatly reduced and pollution, caused by sewage emission, to the environment is reduced; future worries for further development of condensed oil gas are solved.