In this paper, the results of the stable solid-liquid equilibria in the two ternary systems zinc sulfate-copper sulfate-water and zinc sulfate-zinc chloride-water at 323 K and 0.1 MPa were presented based on the method of isothermal dissolution equilibrium. In the experiment, saturated liquid phase and humid residue composition for a series of synthetic brine were determined. At the same time, the corresponding equilibrium solid phases were identified by using the X-ray powder diffraction combined with Schreinemakers' method. Since the foundation of the phase diagram theory concerning a water salt system, the phase diagrams of the two systems were constructed. The results of the experiment reveal that the types of two ternary systems are classified as simple cosaturation type due to the absence of double salt and solid solution. The phase diagram of the ternary system ZnSO4-CuSO4-H2O at 323 K constitutes an invariant point, two univariant solubility curves, and two solid crystalline phase regions corresponding to ZnSO4 center dot 6H(2)O and CuSO4 center dot 5H(2)O. The phase diagram of the ternary system ZnSO4-ZnCl2-H2O at 323 K includes two invariant points, three univariant solubility curves, and three solid crystalline phase regions corresponding to ZnSO4 center dot 6H(2)O, ZnSO4 center dot H2O, and ZnCl2.