The application of ionic liquids as alternatives to conventional organic solvents in the extraction process has been investigated. In the present study, fourteen species of imidazolium-based ionic liquids were added into the NaOH (aq) to remove the mercaptans. The influences of anion species and cation alkyl chain length of the imidazolium-based ionic liquids on the performance of mercaptan removal from light oils have been discussed. The efficiency of extraction for mercaptans exhibited the order of [Ac](-) > [OH](-) approximate to [Br](-) > [BF4](-). The longer alkyl chain imidazolium-based ionic liquids contributed to enhance desulfurization rate of 1-butyl mercaptan. 100% desulfurization rate of 1-butyl mercaptan was achieved by the anion of Ac- ionic liquids and NaOH (aq) at a volume ratio of 40: 1 (V(oil): V(ionic liquid)) and a short equilibrium time within 10 min. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.