A series of cobalt-cerium mixed oxide catalysts (Co 3 O 4 -CeO 2 ) with a Ce/Co molar ratio of 0.05 were prepared by co-precipitation (with K 2 CO 3 and KOH as the respective precipitant), impregnation, citrate, and direct evaporation methods and then tested for the catalytic decomposition of N 2 O. XRD, BET, XPS, O 2 -TPD and H 2 -TPR methods were used to characterize the catalysts. Catalysts with a trace amount of residual K exhibited higher catalytic activities than those without. The presence of appropriate amount of K in Co 3 O 4 -CeO 2 may improve the redox property of Co 3 O 4 , which is important for the decomposition of N 2 O. When the amount of K was constant, the surface area became the most important factor for the reaction. The co-precipitation-prepared catalyst with K 2 CO 3 as precipitant exhibited the best catalytic performance because of the presence of ca. 2 mol% residual K and the high surface area. We also discussed the rate-determining step of the N 2 O decomposition reaction over these Co 3 O 4 -CeO 2 catalysts. #