An eutectic ionic liquid(EIL),choline chloride/oxalic acid,was synthesized and its structure was characterized with FT-IR spectroscopy and ~1H-NMR. The denitrogenation performance of the EIL was investigated in detail using model oil and coker diesel oil as feedstock. Experimental results show that the removal efficiencies of quinoline and indole are almost 100% and 88.05%,respectively at 30 ℃ with the EIL to oil ratio of 1 ∶7(mass ratio),extraction time of 30 min and settling time of 2 h. It is also found ...