The stable phase equilibria of the ternary system CaCl2-SrCl2-H2O and the quaternary system KCl-CaCl2-SrCl2-H2O at 373 K were investigated by means of the isothermal dissolution equilibrium method. According to experimental results, the phase diagrams of the two systems were plotted. The results show that the ternary system CaCl2-SrCl2-H2O at 373 K belongs to the simple cosaturated type, without complex salt or solid solution. There are one invariant point, two univariant curves, and two crystallization fields (where the solids are SrCl2 center dot H2O and CaCl2 center dot 2H(2)O). The quaternary system KCl-CaCl2-SrCl2-H2O at 373 K has a double salt, chlorocalcite (KCl center dot CaCl2). The phase diagram contains two invariant points, five univariant curves, and four crystallization fields (where the solids are KCl, CaCl2 center dot 2H(2)O, SrCl2 center dot H2O, and KCl center dot CaCl2).