The invention discloses a method for synthesizing aromatic aldehyde under normal pressure through palladium catalysis, and belongs to the technical field of catalytic synthesis. According to the method, a palladium-catalyzed aryl halide and normal-pressure carbon monoxide is directly subjected to reduction coupling to prepare aromatic aldehyde in a polyethylene glycol solvent or a water solution of polyethylene glycol under the action of alkali and a reducing agent without needing participation of a ligand. The method for preparing aromatic aldehyde through a catalytic reduction coupling reaction has the advantages that the ligand is not needed, and the activity is good; the reaction is conducted at room temperature under the normal pressure, and the selectivity is high; a substrate is wide in source and stable; the compatibility of substrate functional groups is good, and the application range of the substrate is wide; a reaction medium is green and can be recycled. Under the optimized reaction conditions, the target product separation yield reaches up to 92%.