The invention relates to a method for synthetizing mono-thioether compound. The technical scheme adopted by the invention is as follows: in the presence of carbon monoxide and water, disulfide compound and halogenated hydrocarbon compound are used as raw materials, selenium is used as catalyst, organic base or inorganic base is used as cocatalyst or any cocatalyst is not added, the raw materials react in organic solvent at 20-100 DEG C under atmospheric pressure for 1-24 hours, the product is cooled to the room temperature, then carbon monoxide is displaced by air, stirring is performed for 0.2-2 hours, filtration is performed, distilled water and cyclohexane are used to extract the filtrate, and the solvent in the extract liquor is distilled out through reduced pressure distillation to obtain the target product. The method is convenient and safe to operate, adopts one-pot reaction, has common raw materials, no pollution, high selectivity and high yield; and the catalyst can be separated and recycled after the reaction.