The solubilities of pimelic acid in ionic liquids [EMIM][HSO4], [PMIK]B-r, [i-PMIM][HSO4], [BMIM]B-r, and [BMIM][HSO4] are determined with the suitable experimental methods and apparatus. The experimental data of solubilities are correlated with the Apelblat equation. The solubilities correlated by the model are in good agreement with experimental data.