Abstract: 1-methylnaphthalene/amylbenzene and tetralin were cracked in micro-pulse reactor，respectively and the contents of alkylnaphthalenes in products were determined using GC-MS. It is found that the amount ofαandβposition isomers are increased with increase of reaction conversion and the variation of conversion can be reflected by the ratio of alkyl substituent naphthalenes at different position. Further results confirm that the naphthalene alkylation follows the same mechanism in different reaction systems and is affected by the pore structure of the catalyst used. Hydrocarbon fingerprint information was extracted from the reaction products of five different vacuum gas oils, and the results show that the fingerprint of alkylnaphthalene and alkylphenanthrene can both be used as indicators of cracking conversion.