The (liquid+liquid) equilibrium for the {polyethylene glycol dimethyl ether 2000 (PEGDME2000)+di-sodium hydrogen citrate+H2O} system was studied at T=(298.15, 308.15 and 318.15)K and atmospheric pressure (≈85kPa). The free energies, enthalpies and entropies of cloud points were calculated in order to investigate the driving force formation of this two-phase system. To investigate the effect of molar mass of the polymer on the binodals and tie-lines, similar measurements were also made at T=298.15K on this two-phase system consisting of the PEGDME with molar masses of 500 and 250g⋅mol−1. The effective excluded volume model was used for representation of the phase-forming ability in PEGDME systems. An empirical and the Merchuck equations with the temperature dependency were used to correlate the binodal curves. The Othmer–Tobias and Bancraft and Setschenow equations, the osmotic virial and the extended NRTL models were used to fit the tie-line data.