Mixed oxides of alumina and magnesia with different MgO content were prepared by wet impregnation method. The physicochemical properties and structures of these synthesized mixed oxides γ-Al 2O 3-MgO were studied with X-ray diffraction (XRD), FESEM, Fourior transform infrared (FTIR), Thermogravimeric analysis (TGA), and BET methods. The point of zero charge of mixed oxides was also determined by salt addition method to explore the effect of MgO contents on the PZC of commercial γ-Al 2O 3. 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 γ-Al 2O 3 and MgO. Further, it was found that the addition of low amounts of MgO to alumina didn't cause change in the structure of alumina however, high loading of MgO caused change in the phase and structure of alumina depending on the MgO loading. Moreover, it was observed that the activation energy of degradation increased as the Mg (NO 3) 2.6H 2O loading was increased onto γ-Al 2O 3.