Three groups of cobalt mixed oxide catalysts(Mg/Zn–Co, Mg/Zn–Ce–C, K/Na–Mg/Zn–Ce–Co)were prepared by sol–gel or impregnation methods. The synergistic effects of transition metal, rare earth metal and alkali metal on cobalt mixed catalysts for nitrous oxide(N2O)decomposing to N2 and O2were investigated. The experimental results revealed that the catalytic activity for N2 O decomposition was promoted as Co2+was replaced partially by Zn2+/Mg2+, moreover, the characterization analysis by XRD and XPS showed that Zn2+/Mg2+replaced Co2+successfully into the spinel structure of Co3O4 and promoted significantly the catalytic activity. Especially, the addition of CeO2 and K2O/Na2O decreased the binding energy and resulted in an increase in the density of the electron cloud around Co and an improvement of the catalytic activity. Of the investigated cobalt mixed catalysts, the best catalytic activity was shown by 2% K–Zn0.5–Ce0.05–Co catalyst. The synergistic effects of transition metal (Mg / Zn-Co, Mg / Zn-Ce-C, K / Na-Mg / Zn-Ce-Co) were prepared by sol- gel or impregnation methods. , rare earth metal and alkali metal on cobalt mixed catalysts for nitrous oxide (N2O) decomposing to N2 and O2were investigated. The experimental results revealed that the catalytic activity for N2 O decomposition promoted promoted as Co2 + was replaced partially by Zn2 + / Mg2 +, moreover , the characterization analysis by XRD and XPS showed that Zn2 + / Mg2 + substituted Co2 + successfully into the spinel structure of Co3O4 and promoted significantly significantly the catalytic activity. Especially, the addition of CeO2 and K2O / Na2O decreased the binding energy and resulted in an increase in the density of the electron cloud around Co and an improvement of the catalytic activity. Of the investigated cobalt mixed catalysts, the best catalytic activity was shown by 2% K-Zn0.5-Ce0.05-Co catalyst.