A study was carried out on the effect of ionic liquids (morpholine formate and aniline formate) on the desulfurization of catalytic cracking gasoline and coking gasoline. A relationship was found between the extent of desulfurization of the gasolines on the ionic liquid:gasoline ratio and the duration of the extraction. An increase in the ionic liquid: coking gasoline ratio from 1 : 10, to 1 : 5, and then 1 : 1 led to enhancement of desulfurization t o 19.5%, 21.5%, and 49%, respectively. An increase in the ionic liquid: catalytic cracking gasoline ratio from 1 : 3 to 1 : 1 led to an increase in the desulfurization of this gasoline from 40.2% to 65.4% for 0.2 h extraction time. When the extraction time was extended to 0.5 h, the desulfurization of catalytic cracking gasoline was enhanced from 50 to 70%.