Mg-substituted La0.8Ce0.2CoO3 (LCCM) perovskite oxides with large surface areas (148.7 m(2)/g) were prepared by a modified citric acid complexation method. Then, K promoted LCCM catalysts were synthesized via impregnation. The samples were characterized by XRD, FT-IR, N-2 adsorption-desorption, SEM, TEM, XPS and TG/DTA techniques. The addition of Mg not only restrained the growth of LCCM crystallite, but also inhibited the agglomeration of nanoparticles and, consequently the surface areas of LCCM perovskites increased. The low-valence ion substitution of Mg2+ both promoted the formation of Co4+ and adsorbed oxygen species, which were further enhanced by the partial replacement of La3+ by K+. The local electron density of neighboring carbon sites and their affinity for binding oxygen atom were promoted by K promotion, which also contributed to the contact between soot and catalyst surface, and the activity of the catalyst was thus enhanced. Among all the catalysts, the K/LCCM-4 calcined at 600 degrees C exhibited the highest activity with T-m,T-t at 380 degrees C, and maintained good stability with T-m,T-l only increased by 10 degrees C after recycling for three times. 2016 Elsevier B.V. All rights reserved.