Abstract: A series of functionalized acidic ionic liquids (ILs) were synthesized and used to remove non-basic nitrogen (indole) in model oil. The results indicate that the anions have a significant impact on the denitrification efficiency; the denitrification rate of the ionic liquids with various anions increases with their acidity, i.e. it follows the order of HSO₄^- > CF₃COO^- > H₂PO₄^- > CH₃COO^-. The effects of IL/oil ratio, IL/H₂O ratio, settlement time, reaction temperature and time on the denitrification efficiency of (CH₃CH₂)₃ N (CH₂)₃SO₃H HSO₄ were well considered. The results showed that 99.12% indole nitrogen in the oil can be removed with (CH₃CH₂)₃N(CH₂)₃SO₃HHSO₄ under the optimum condition; furthermore, the IL exhibits high stability and its denitrification activity remains almost unchanged even after being reused for six times.