Abstract: Based on the commercial result of LTA technology in a refinery of SINOPEC，the conversion rules of the aromatics in hydrotreated LCO（hydro-LCO）catalytic cracking were studied in terms of molecular-based hydrocarbon. The results showed that 73.91% of monocyclic aromatics in products was from cracking reaction of the monocyclic aromatics like alkyl-benzene and naphthenic-benzene in hydro-LCO，and the rest was from the aromatization reactions of non-aromatic compounds including paraffin hydrocarbons and naphthenic hydrocarbons in hydro-LCO in the catalytic cracking process. The contents of dicyclic-aromatics and tricyclic and polycyclic aromatics in products were 37.77% and 18.49%, respectively, and the rests were made up from condensation reactions of monocyclic aromatics and dicyclic aromatics in hydro-LCO. The apparent conversions of alkyl-benzene，hydrocarbons like indane and tetraline and hydrocarbons like indene in catalytic cracking processing were 82.50%，93.80% and 80.72%, respectively. The results can be used to guide the further improvement of LTA technology and proprietary catalyst.

Key words: light cycle oil, hydrotreating, catalytic cracking, LTA, aromatics