Ionic liquids have such unique properties as a low vapor pressure close to zero and trivial volatility, making them green solvents and good substitutes for volatile and toxic organic solvents. These materials, in addition to serving as a solvent, can act as an active catalyzer in the reactions. Nowadays, the use of ionic liquids is common for dissolve and functionalizing such polysaccharides as cellulose and starch, but these materials have not yet been used for finishing cotton fabrics. It has been attempted in this study to investigate the possibility of synthesizing inexpensive bronsted acidic ionic liquids and using them for desizing cottons fabrics having starch size. To this aim, morpholine, sulfuric acid and hydrochloric acid were employed and ionic liquids of morpholinium hydrogen sulphate and morpholinium chloride were synthesized. Then, under different conditions in terms of temperature, concentration and time, desizing of cotton clothes was investigated. Also, to further probe the influential parameters on the quality of desizing using the ionic liquid of morpholinium hydrogen sulphate and find the optimal conditions, a design of experiment using response surface method was conducted. Samples desized using ionic liquid, under optimal conditions, were compared with those desized by the conventional enzymatic methods. To investigate the result of ionic liquids synthesis, Fourier transform infrared spectroscopy, and to analyze the changes in starch granules in solutions, optical microscope were used. In order to measure the quality of desizing in the samples, starch test (tegewa), weight loss percentage and images taken from scanning electron microscope were used. Also, the effect of desizing on the strength, whiteness and yellowness indexes, water and direct dye absorption of the fabric and concentration of mineral metals present in the structure was investigated. The results of experiments showed that by using the ionic liquids, it was possible to achieve desizing the cotton fabric with good quality (tegewa degree of 6 and above), while not affecting the strength. The samples desized by morpholinium hydrogen sulphate under optimal conditions had a quality comparable to those desized by the conventional enzyme method. On the other hand, as another advantage of using ionic liquid over ?-amylase enzyme, it was found that full wettability of desized samples made it possible to eliminate the common step of alkaline scouring and considerably reduce the mineral metals making problems in the subsequent finishing processes. Key words : Ionic liquid, cotton fabric, pretreatment, desizing, starch