For the Co3O4/CaCO3 catalysts used for N2O decomposition, the activity of the catalyst prepared by stepwise precipitation is much superior to the catalysts prepared by impregnation or coprecipitation in the same composition. HRTEM observation and EDX analysis indicate that the stepwise precipitation leads to cobalt existing as little Co3O4 crystallites tightly bound to the CaCO3 particles. The special structure made the Co3O4 ideal accessibility and better interaction with the support in the catalyst, and the CaCo2.5(SP) catalyst with this structure is much more active than the CaCo2.5 catalyst reported in literature prepared in traditional method. At 300 degrees C, N2O in the feed gas 2000 ppmv N2O/Ar was completely converted over the CaCo2.5(SP) at 20,000 h(-1). Moreover, the CaCo2.5(SP) catalyst exhibited better resistance to sintering at 800 degrees C and quite high activity under the presence of 5 vol% O-2 and 2 vol% H2O at 350 degrees C as well.