Butyl acetate synthesis in imidazolium ring-based ionic liquids (ILs) containing trifluoromethanesulfonate, [TfO]. using Candida antarctica lipase B was demonstrated. Among the ILs tested, the highest butyl acetate production and its initial rate was achieved in [Bmim][TfO]. Compared with tert-butanol, which has been the conventional solvent for transesterification reactions, the initial reaction and conversion rate were approximately 1.4 and 1.1 times, respectively, higher. Some physicochemical parameters, such as viscosity, hydrophobicity, and partial charge of ILs were examined to find the relations which influence reaction rates. Although only weak correlations between each parameter and enzyme activity were found, it shed a light on understanding the generalization complexity of ILs for enzyme reaction.