The equilibrium data of quaternary system phosphoric acid + sodium chloride + water + tri-n-butyl phosphate (TBP) was discussed at 298.15 K and atmospheric pressure. It was investigated experimentally in the mass concentration range 0-15% of NaCl and 4-24% of H3PO4 in the initial aqueous phase. The experimental results show that the separation factor of H2O and the distribution coefficient of H3PO4 increase when the content of H3PO4 increases. The separation factor of NaCl decreases after an increase to a maximum value. Moreover, it was found out that the mass ratio of ternary system H3PO4-NaCl-H2O to the saturation point. It would separate easily at when the mass percent of NaCl occupies more than 12% in the system. The experimental tie-line data was correlated with the nonrandom two-liquid activity 0.0 coefficient model.