In this work CuO/MgO/Fe3O4 nanocomposite was synthesized by the solgel pyrolysis method. Characterization of the samples was performed by the X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR). The photocatalytic activity of CuO/MgO/Fe3O4, evaluated using the photodegradation of methylene Blue (MB) as a probe reaction under the irradiation of Xenon light. The dye photodecolorization process was studied considering the influence of experimental parameters such as catalyst concentration, CuO/MgO/Fe3O4 ratio and pH on methylene blue adsorption rate. The maximum photocatalytic activity of the CuO/MgO photocatalyst was observed to be calcined at 450°C for 3 h (the molar ratio of Cu to Mg was 1:2) due to the sample with good crystallization and high surface area. The complete photodecolorization of a1×10-5mol L-1methylene blue solution, at pH =10 and roomtemperature was achieved in less than 20 min.Experimental results showthatCuO:MgO:Fe3O4 (30:50:20) nanoparticles possess high photocatalytic activity at compression of universal catalysts.