This work focuses on the extension of group parameters and application of the group-contribution lattice-fluid equation of state (GCLF EOS) for the systems with ionic liquids (ILs). The new group parameters e(kk) and R-kk for ILs in GCLF EOS were obtained by means of correlating the liquid density of pure ILs at different temperatures, while the group binary interaction parameters alpha(mn) were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ILs at different temperatures, which were exhaustively collected from references. New IL groups were added into the current parameter matrix. It was verified that GCLF EOS for ILs can be used for predicting liquid densities of pure ILs or the mixture of IL and solute, vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) at finite concentration, as well as identifying the structure-property relation in separation science. This is the first work for us to extend the predictive GCLF EOS to the systems with ILs. (c) 2012 Elsevier Ltd. All rights reserved.