The (solid + liquid) phase equilibria of the NaBr + KBr + SrBr2 + H2O quaternary system and two subsystems (NaBr + SrBr2 + H2O and KBr + SrBr2 + H2O) were studied at T = 323 K using the isothermal dissolution method. With the solubility values of each system, the stable phase diagrams of these systems were drawn. It shows that there is neither solid solution nor double salt in the diagrams. The three systems are all of the hydrate type I, and only one invariant point is found in the phase diagrams of the three systems.