The reactivity and selectivity to 2,6-dialkylnaphthalene were affected by the polarity of solvent, alkylating agent, reaction time and reaction temperature in the selective isopropylation of naphthalene or 2-methylnaphthalene（2-MN） with AlCl₃ catalyst. Reaction with isopropylbromide as an alkylating agent in non-polar solvents(hexane or isooctane) was found to be a good system for the higher activity and selectivity to 2,6-dialkylnaphthalene. The reactivity and selectivity were increased as increasing the reaction time and temperature(between 4℃ and 60℃). When 2-MN was used as a substrate, the selectivity to 2,6-DIPN was 2 times higher than naphthalene was used.