A series of mixed oxides of alumina and magnesia with different MgO contents were prepared by wet impregnation method. The synthesized mixed oxides Al 2O 3-MgO were characterized with X-ray diffraction (XRD), FESEM, Fourior Transform infrared (FTIR), Thermogravimeric analysis (TGAJ, and BET methods. The point of zero of mixed oxides was determined by salt addition method to explore the effect of MgO contents on the PZC of commercial AITOJ. The activation energies of thermal decomposition for different Mg (NO 3) 2):.6H 2O) loading onto Al 2O 3 was determind by Freidman model. The results showed the as the MgO loading was increased the PZC of alumina was also increased linearly. Moreover, the PZC of these synthesized mixed oxides varied between the PZCs of pure oxides of 2O 3 and MgO. Further, it was noted that alumina retained its structure when the MgO content was low however, high loading of MgO caused change in the phase and structure of alumina. Activation energy of thermal degradation increased as the Mg (NO 3) 2.6H 2O loading was increased onto Al 2O 3.