Macroporous Co3O4-MgO composites with uniform pores of 0.3-1.0 mu m were successfully fabricated for the first time by the sol-gel method using poly(methyl methacrylate) (PMMA) particles as a template. The macropore size and BET surface area were easily controlled by selecting a proper size of the commercial PMMA microspheres. In addition, the composites showed smaller Co3O4 particles than the catalysts prepared by the conventional impregnation method. High surface area composite catalysts with controlled porous structure exhibited a higher methylene blue degradation activity in the presence of Oxone as an oxidant than conventional supported catalysts. Because good dispersion of the active Co3O4 species is a key factor to enhance the catalytic activity, this finding could be attributed to the good mixing of Mg and Co precursors, a distinct advantage of the sol-gel technique.