Wastewater containing sodium carbonate and sodium fluoride will be generated in the rare earth extraction process and the preparation process of sodium fluoride.The phase equilibrium of the ternary system of Na₂CO₃-NaF-H₂O was studied to provide theoretical guidance for the preparation of practical production and recovery of sodium fluoride and sodium carbon-ate.The isothermal dissolution equilibrium method was used to study the phase equilibrium relationship of the ternary system of Na₂CO₃-NaF-H₂O at 298.15 K and 318.15 K.The solubility of each component of the system and the density and pH of the equilibrium liquid phase were measured.The phase diagram and the relationship between physicochemical parameters and content of component were drawn according to the solubility data.The solid phase was analyzed and characterized by X-ray diffraction（XRD）.The experimental study showed that the system had no double salt and solid solution,and belonged to the I-type phase diagram of hydrate.The phase diagram included 1 all-liquid region,2 single-salt crystallization regions,1 mixed crystallization region,1 all-solid region,3 univariate solubility curves,and 1 co-saturation point.Na₂CO₃ had a strong salting-out rate for NaF.When the temperature was constant,the mass fraction of Na₂CO₃ was higher,the density was greater,and the pH of the solution was greater.When the mass fraction of Na₂CO₃ was constant,the temperature was higher,the density was greater,and the pH of the solution was lower.