Abstract: A series of alkylimidazolium perchlorate type of ionic liquids (ILs) with different length of alkyl chains were synthesized using N-methylimidazolum, n-alkyl bromide, sodium perchlorate as raw material. The desulfurization of the model or real oil using ILs was investigated under different conditions. The results show that the best desulfurization rate is obtained after 50 min under the condition of [C6mim]ClO4:oil=4:1(v/v), 60℃, using [C6mim]ClO4 as extracting reagent. The sulfur removal reaches 86.90 % for the model oil ([S]0=1164μg/g). When the volume ratio between IL and fuel oil is 1:1, the sulfur removal is 65.24% for the FCC gasoline ([S]0=117μg/g) and 58.05% for the FCC diesel ([S]0=1974μg/g). After the reaction, the fuel oil and ionic liquid can be separated simply by decantation. The ILs used can be purified by fractional distillation and recycled at least for 5 times without significant loss of activity.