Phase equilibria of the quaternary systems (KCl + CaCl2 + SrCl2 + H2O) and (LiCl + NaCl + SrCl2 + H2O) at 288.15 K and 0.1 MPa were studied using the isothermal dissolution method, and the phase diagrams of the two systems mentioned above were plotted. There are two invariant points and four crystallization regions in the quaternary system (KCl + CaCl2 + SrCl2 + H2O). Besides the crystallization regions of the minerals KCl, CaCl2 center dot 6H(2)O, and SrCl2 center dot 6H(2)O, the solid solution (Ca,Sr)Cl-2 center dot 6H(2)O was found. The strontium and calcium salts can be separated from each other by avoiding crystallization in the solid solution region. There are two invariant points and four crystallization regions corresponding to NaCl, SrCl2 center dot 6H(2)O, SrCl2 center dot 6H(2)O, and LiCl2 center dot 6H(2)O in the quaternary system (LiCl + NaCl + SrCl2 + H2O). Lithium chloride has a strong salting-out effect on NaCl and SrCl2 center dot 6H(2)O. The experiment results of the quaternary systems (KCl + CaCl2 + SrCl2 + H2O) and (LiCl + NaCl + SrCl2 + H2O) have a significant value for separating and purifying minerals from the oilfield brine in the Nanyishan Section of the Qaidam Basin.