The binodal data for an aqueous two-phase system (ATPS) containing 1-alkyl-3-methylimidazolium tetrafluoroborate ([C(n)mim]BF4, n = 2, 3, 4) or 1-alkyl-3-methylimidazolium chloride ([C(n)mim]Cl], n = 2, 4, 6, 8, 10, 12) and inorganic salts (K2HPO4, NaH2PO4, (NH4)(2)SO4, and NaCl) or organic salts (sodium citrate, sodium tartrate, and sodium acetate) were widely determined at T = 298.15 K. The various binodal curves could be fitted and summarized as two kinds of empirical nonlinear equations with the lowest standard deviation (SD). The effects of the salt type and cation alkyl chain length of the ionic liquid (IL) on ATPS binodal curves were further discussed. It was displayed that the salting-out ability of different salts was a major factor in these ATPS formations. For [C(n)mim]BF4-based ATPS, the salting-out ability of various salts decreased in the following order: (NH4)(2)SO4 > Na3C6H5O7 > Na2C4H4O6 > NaH2PO4 > NaC2H3O2 > NaCl. For the [C(n)mim]Cl aqueous solution, only K2HPO4 or (NH4)(2)SO4 could cause the phase separation and formed ATPS, and the salting-out ability of K2HPO4 was stronger than the effect of (NH4)(2)SO4. The phase separation abilities of the researched [C(n)mim]BF4 in the corresponding ATPS increased with the increase of cation alkyl chain length, while [C(n)mim]Cl had the best phase separation ability of the researched [C(n)mim]Cl-based ATPS.