Aluminum-ferric separation has attracted significant interest in the field of hydrometallurgy. Using phase equilibria theory, fractional crystallization and separation of a mixed salt solution is a relatively effective method. The phase equilibria of the ternary system or tertiary system AlCl3-FeCl3-H2O(-HCl) at 298.15 K for different H+ concentrations were studied using the isothermal dissolution equilibrium method, and plotted the corresponding phase diagrams and density diagrams. The experimental results show that with increasing H+ concentration, the solubility of AlCl3 decreased from 31.20 to 0.13%, and the crystallization region of AlCl3 center dot 6H(2)O gradually increased. H+ concentration had little influence on FeCl3 solubility, and the solubility of FeCl3 was 47.52%. Through theoretical calculations, the desired amount of water to evaporate and crystal precipitation can be obtained through the calculation model for the system composed of different materials. The route is designed by the phase equilibrium and the phase diagram theory, and the separation of aluminum and ferric from aluminate acid leaching solution of coal gangue in literature. The direct yield of AlCl3 center dot 6H(2)O obtained by evaporation and crystallization was 77.15%, and the purity reached 99.81% after rinsing with concentrated hydrochloric acid.