Abstract: Imidazolium chloride were synthesized via substitution reaction between N-alkylimidazole and dichloroalkane, then AlCl3 was added to complex to prepare seven chloroaluminate dication ionic liquids. The prepared ionic liquids were used to catalyze the condensation reaction between triethyl orthoformate and diethyl malonate to synthesize ethoxymethylenemalonate diethyl ester. The acidity of ionic liquids were measured by IR. The proposed reaction mechanism was analyzed by detecting the morphology of aluminum in catalysts by 27Al NMR. The effects of catalyst type, catalyst dosage, ratio of materials to solvent, reaction temperature, reaction time and catalyst recyclability on the reaction were investigated. The optimal process conditions were using 1,6-bis(N-methylimidazolyl)hexane chloroaluminate ionic liquid 〔[C6(Mim)2]Cl2-4AlCl3〕 as catalyst with its dosage of 0.8% (calculated based on molar amount of diethyl malonate), the molar ratios of triethyl orthoformate to diethyl malonate and to acetic anhydride at 1.75∶1.00∶2.50, with program temperature at 100 ℃ for 2 h and 140 ℃ for 6 h.Under these conditions, the conversion of diethyl malonate reached up to 98%, selectivity and yield of target product were 98% and 97%.