The general steps for synthesizing 3,4'-dichlorodiphenyl ether from p-chlorophenol and 1,3-dichlorobenzene are as follows: first, the organic solvent was prepared by mixing ionic liquid with dipropylene glycol methyl ethyl ether in a mass ratio of 1:20. The specific synthesis method is as follows: (1) A copper salt catalyst is added to the reaction system, while 1,3-dichlorobenzene, p-chlorophenol, a base and the organic solvent prepared above are mixed. Among them, the molar ratio of 1,3-dichlorobenzene, p-chlorophenol, potassium carbonate base and cuprous chloride salt was 6:1:1.2:0.01, and the total dosage of organic solvent was 10% of the total amount of the reactants; (2) under microwave-catalyzed conditions, the reaction mixture was stirred for 2 hours at 500 W power, and the temperature of the reaction was controlled at 60~110°C. The reaction temperature was controlled at 60~110°C. The reaction temperature was set to 0.01 °C for 2 hours. After the reaction was completed, the mixture was left to cool, filtered, and the filtrate was distilled under reduced pressure to collect a colorless and transparent liquid product. The conversion of the method was 99% and the yield was 93%.