To evaluate the anion-cation and ion-solvent interactions of ionic liquids (ILs) in solvents, a series of theoretical calculations were performed in different mediums (water, dimethyl sulfoxide, acetonitrile, methanol, ethanol, acetone, dichloroethane, and chloroform). The obtained results suggest that the solvent has remarkable influence. The corresponding interaction energies decrease with the increase of the solvent dielectric constant. There exists obvious difference between the solvation energy of ionic pairs and separated ions, which is the reason for the influence of solvents on the binding energy. The geometric structure, charge, and dipole moment of the ILs were also influenced regularly by solvents. (C) 2011 Elsevier B.V. All rights reserved.