Phase equilibrium of aqueous two-phase systems (ATPS) containing UCON 50 HB-2000 + potassium phosphate and UCON 50 HB-2000 + sodium citrate were investigated in this work. The effect of temperature and type of salt were determined at (277.15, 298.15, and 313.15) K in pH 6.0, 7.0, and 8.0. Increasing the temperature of the phase system leads to an increase in the slope of the tie-line (STL) and in the tie-line length (TLL) causing a shift in the binodal position toward the origin. Sodium citrate showed a better capability to induce phase separation than potassium phosphate.