The invention discloses a supported ionic liquid catalyst. The supported ionic liquid catalyst is characterized in that imidazole is immobilized onto chloromethylated FDU mesoporous phenolic resin by nucleophilic reaction and reacts with halides containing different functional groups to prepare a mesoporous material supported functional imidazole type ionic liquid catalyst. The preparation of the catalyst comprises the following steps: chloromethylation of a mesoporous material, imidazolation and supporting of ionic liquid. The catalyst is used for synthesizing a cyclic carbonate by cyclic addition reaction of carbon dioxide and an epoxy compound, and the using quantity of the catalyst is 0.1-2mol% of the liquid content of the epoxy compound. Compared with the prior art, a large number of hydroxyl groups exist in the mesoporous material, and the supported ionic liquid catalyst has the double advantages of an inorganic mesoporous material and an organic polymer, as well as large specific surface area, adjustable pore structure, good hydrophobicity and chemical stability, high catalytic activity, good chemical selectivity, easiness in separation and recovery, mild reaction conditions, environmental friendliness and easiness in industrial implementation.