The invention relates to a method for synthesizing an asymmetric diaryl mono-selenide compound. The method comprises the following steps: taking aryl carboxylic acid and aryl iodide as reaction materials under oxygen conditions in an organic solvent, taking elemental selenium as a selenium based reagent, carrying out a cascade reaction under the combined promotion action of a copper catalyst, a ligand and alkali, thereby obtaining the asymmetric diaryl mono-selenide compound. The method is cheap and readily available in aryl carboxylic acid substrate, aryl iodide and copper catalyst, wide in substrate range, simple in reaction conditions and high in product yield and purity, develops a novel synthetic route and method for the asymmetric diaryl mono-selenide compound and has excellent application potential and research value.