This work describes the solid-liquid phase equilibria in the ternary system SrCl2-SrBr2-H2P at T = 273, 298, and 323 K based on the method of isothermal dissolution equilibrium. Since saturated liquid phases and humid residue compositions for a series of synthetic brines were determined simultaneously, the measured equilibrium tie lines were constructed. At the same time, the corresponding equilibrium solid phases were identified by using the Schreinemakers' method supplemented with X-ray powder diffraction. The experimental phase diagrams of the system SrCl2-SrBr2-H2O at T = 273, 298, and 323 K were established according to the theory of phase diagram for water salt system. It is found that the type of the system is classified as completely solid solution type due to formation of solid solution Sr(Cl, Br)(2)center dot 6H(2)O. The phase diagrams of the ternary system SrCl2-SrBr2-H2O at 273, 298, and 323 K are constituted of one univariant solubility curve and one solid crystalline phase region corresponding to Sr(Cl, Br)(2)center dot 6H(2)O, without any invariant point. The Pitzer equation was selected to calculate the solubility data in the ternary system SrCl2-SrBr2-H2O at T = 273, 298, and 323 K. The solubility modeling approach achieved good agreement with experimental solubility data.