Abstract: The Cu-containing ionic liquids (IL), like BMImCl-1.8AlCl₃-0.5CuCl and Et₃NHCl-1.8AlCl₃/ CuAlCl₄, were synthesized and characterized. The selectivity of isobutene/butene alkylation of Cu-containing IL was also investigated. The results showed that the selectivity had little relation to the acidity of Cu-containing IL. The research octane number (RON) of Et₃NHCl-1.8AlCl₃/CuAlCl₄ alkylate could be higher than 100, which was better than those obtained by sulfuric acid, common chloroaluminate IL, and composite IL under the identical reaction conditions. The complexation of CuAlCl₄ with 2-butene in alkylation process should be accounted for the super selectivity of trimethylpentane (TMP) of isobutane alkylation catalyzed by Cu-containing IL.