The anticipated depletion of petroleum reserves in the next few decades has led to intense interest in the use of lignocellulosic biomass as the feedstock for both biofuels and chemical products. Nowadays, the most common biofuel is ethanol derived from corn grain and sugar cane. It is expected that there will be limits to the supply of these raw materials in the near future. Therefore, lignocellulosic biomass, including agricultural residues, is considered as an attractive feedstock for the future supplies of ethanol. Lignocellulosic biomass is highly recalcitrant and various pretreatment techniques are needed to facilitate its effective enzymatic hydrolysis to produce sugars for further conversion to bio-based chemicals. Ionic liquids are of interest in pretreatment because of their potential to dissolve lignocellulosic materials. In this study, two morpholinium based ionic liquids N -Allyl- N -methylmorpholine acetate and Morpholine acetate were synthesized and then with different percentages of DMSO used for pretreatment of rice straw prior to enzymatic hydrolysis. Pretreatment was performed at 90, 100 and 120 °C for 2, 3 and 5 hours with 5% solid loading. Also, in order to compare the performance of the ionic liquids in the pretreatment, four solvents, i.e., NMO 85% , [Bmim][OAc], NaOH 8% , and H 3 PO 4 85% , were used for the pretreatment of rice straw. To evaluate the effect of pretreatment, enzymatic hydrolysis and fermentation of pretreated and untreated rice straws was performed at 45 °C and 32 °C, respectively. The results of the enzymatic hydrolysis samples pretreated with N -Allyl N -methylmorpholine acetate showed that glucan was almost completely converted to glucose and hydrolysis yield was increased from 37.3% for untreated rice straw sample to 98.6% for pretreated samples. Furthermore, the results of the fermentation indicated that ethanol yield was improved from 36.1% for untreated rice straw to more than 85% for samples pretreated with N -Allyl N -methylmorpholine acetate at 120 °C. The results of enzymatic hydrolysis and fermentation demonstrated that using Morpholine acetate is not suitable for the pretreatment of rice straw. Moreover, the use of co-solvent at high temperature could help to minimize the consumption of the ionic liquids without lowering their performance and increase the pretreatment efficiency due to the viscosity reduction effect. Key Words: Pretreatment, Ionic Liquids, Dimethyl Sulfoxide, Rice Straw, Enzymatic Hydrolysis, Bioethanol.