The invention relates to a chemical synthesis process and particularly relates to a method for synthesizing 2-chloropropionaldehyde. In the method, chloralkane is used as a solvent, acid is used as a catalyst, chlorine gas is used a chlorine source, propionaldehyde is used as a raw material, and the dosage of the acidic catalyst used in the invention is a catalytic dosage, so that the problem of high acidity of a product during after-treatment is solved; the reaction condition is mild, and no problems such as temperature runaway and the like exist; the reaction time is short; almost no water or a small deal of water is contained in a chlorination liquid, so that the complex dewatering operation during the after-treatment is avoided; and the product is high in purity and yield and few in three wastes.