Abstract: The stable phase equilibria of the ternary system KCl+CaCl₂+H₂O at 278.2 K and 308.2 K were investigated by isothermal dissolution equilibrium method. The solubilities, densities, and refractive indices of the aqueous ternary system were determined, the corresponding solid phases were identified by Schreinemakers wet residue method and X-ray diffraction. The results show that the ternary system KCl+CaCl₂+H₂O at 278.2 K and 308.2 K are both simple types, without double salt or solid solution formed. The stable phase diagram of the ternary system consists of one invariant point, two isothermal dissolution curves, and two crystallization zones corresponding to two single salts CaCl₂·6H₂O and KCl. By comparison of the stable phase diagrams at 278.2 K, 308.2 K, and 348.2 K shows that the crystallization region of KCl is largest at 308.2 K, which means that it is most easily precipitated from the chloride type solution with potassium and calcium. The crystallization form of calcium chloride changes from CaCl₂·6H₂O to CaCl₂·2H₂O with temperature increase.