Abstract: NiCoAl ternary mixed oxides derived from hydrotalcite-like compounds (HLc) with (Ni+Co)/Al atomic ratio of 3 and Ni/Co of 0.2 were incipiently impregnated by potassium carbonate solution to prepare K-promoted NiCoAl mixed oxides for catalytic decomposition of N₂O. The effects of catalyst preparation parameters such as K loadings, calcination temperatures, and reaction atmospheres on catalytic activity were investigated. The catalysts were characterized by BET, XRD, H₂-TPR, and XPS techniques. The results show that the catalytic activity of NiCoAl mixed oxides is largely enhanced by the addition of K species in the presence of oxygen and steam, and the optimal catalyst preparation parameters are K/(Ni+Co) atomic ratio of 0.05 and calcination temperature of 400℃. XPS and H₂-TPR data show that the electron binding energy of active Co₃O₄ and NiO species over K-promoted catalysts surface shifted to lower value, indicating the surface Co-O and Ni-O bonds were weakened, thus the reduction peaks of Co³⁺ to Co²⁺ and Ni²⁺ to Ni⁰ moved to lower temperature, and the catalytic activity and resistance towards water is improved.