In the present work report, the MgAl2O4and the Ag/MgAl2O4 samples were successfully synthesized by the modified hydrothermal and the isovolumetric impregnation methods, respectively. The structural properties of the prepared samples were systematically characterized by XRD, SEM, TEM, DRS, XPS and et al techniques. The photocatalytic degradation of methylene blue by the Ag/MgAl2O4 and MgAl2O4 samples was comparatively studied under UV lamp irradiation. The results revealed that the prepared Ag/MgAl2O4 (pH=6) samples were the most active among the samples in photocatalytic of methylene blue. Under UV lamp irradiation, the Ag/MgAl2O4 (pH=6) photodegradation of methylene blue reached to 89.6% within 120 min. And the Ag/MgAl2O4 (pH=6) complex photocatalysts displayed a high photochemical stability under repeated irradiation. Repeated irradiate the Ag/MgAl2O4 (pH=6) compound, which indicated it had a high photochemical stability.