The present invention relates to a method for synthesizing a benzyl bromide compound directly from isotope labeled benzene rings, the steps are as follows: (1), mixing carbon tetrachloride, paraformaldehyde and concentrated sulfuric acid in sequence, then adding hydrobromide, heating, adding isotope-labeled benzene, isotope-labeled mono-substituted benzene or isotope-labeled multi-substituted benzene, wherein the isotope is labeled as deuterium, tritium, 13C or 14C; then stirring for 4 to 20 hours; (2), cooling the reaction solution to 20-30 DEG C, and then washing with water, saturated sodium bicarbonate and water in sequence, extracting aqueous phase with dichloromethane, after standing and layering, separating the lower layer organic matter, namely a crude benzyl bromide compound. The method has the advantage of direct use of the most basic benzene-ring-labeled source benzene or aromatic hydrocarbon as a raw material for one-step synthesis of the benzyl bromide compound, and the synthesis process is simple and safe.