Ionic liquids have been widely introduced in various engineering applications, including absorption cooling systems. The use of ionic liquids as sorptive media in absorption systems is intended to improve the system performances by removing the disadvantages of conventional working fluids. Although theoretical investigations based on solubility of refrigerant/ionic liquid mixtures show a competitive performance, heat transfer and mass absorption performance, which is also an important key of system, remains open. This paper theoretically studies the absorption process of refrigerant in ionic liquid to obtain the most prominent ionic liquids for absorption machines, both in terms of thermodynamic and heat and mass transfer performance. The results are analyzed, and the performances are compared with conventional working fluid. For instance, in the case of water/[dmim][DMP], the heat transfer performance is higher, but its lower solubility and diffusivity gives less absorption rate than water/LiBr working fluid.