The activities of the Cu-Cr-Mg-Al catalysts in the dehydrogenation of cyclohexanol to cyclohexanone were correlated with particle sizes and the reducibility of the copper species based on XRD and TPR characterizations. Cu-0 was proven to be the active center of the catalysts calcined at low temperatures and some solid solution (MgCu2O3) and spinel (CuAl2O4 or MgAl2O4) were produced when the calcination temperature reached 1,000 A degrees C. The Cu-Cr-Mg-Al catalyst prepared by the co-precipitation method and calcined at 400 A degrees C showed the best activity, with a conversion of 79.7% and a selectivity of 98.6% at 300 A degrees C.