The invention belongs to the field of chemical synthesis, particularly a preparing method of deuterated aromatic compounds. The method includes subjecting an aryl halide, as an initial raw material, to a palladium catalyzed carbon-halogen bond reduction reaction in which deuterium anion participates at 60-100 DEG C under inert gas protection to synthesize a target compound, with deuterated sodiumformate being adopted as a deuterating agent, dimethyl sulfoxide being adopted as a solvent, metal palladium being adopted as a catalyst and organphosphorus being adopted as a ligand. The method is mild in condition, avoids the use of expensive deuterating agents as a solvent in a reaction process so that the production cost is reduced, and is suitable for large-scale production. The deuteration rate of the compounds reaches 98% or above, and the compounds can be applied in the field of organic optoelectronic materials, medicines, pesticides, and the like.