Massive emissions of CO2 have caused environmental problems all over the world. The fixation of CO2 into cyclic carbonates is regarded as an effective way of capturing and utilizing CO2. Ionic liquid catalysts (ILCs) have received great attention and been employed for catalyzing the above reaction in recent years due to their unique properties. However, there are still a few problems requiring solutions in order to finally find the “ideal catalyst”. Herein, we reviewed a number of recent related literature. The progresses of both homogeneous and heterogeneous ILCs were discussed to find out where we are and which directions to work on. The effects of cations and anions of ionic liquids (ILs), functional groups, reaction phase states, structures of supports, preparation methods of supported ionic liquids (SILs), and interactions between the ILs and supports were investigated systematically. Accordingly, basic principles of designing ILCs for the title reaction are summarized and directions of future investigations are highlighted. Designing ILs: Homogeneous and heterogeneous ionic liquid catalysts for the cycloaddition reaction of CO2 and epoxides to synthesize cyclic carbonates were reviewed. The effects of cations and anions of ionic liquids, functional groups, reaction phase states, structures of supports, preparation methods of supported ionic liquids, and interactions between the ILs and supports were investigated. Accordingly, basic principles of designing ionic liquid catalysts for the reaction were summarized.