The stoichiometric LaCoO3 and nonstoichiometric LaCo1.2O3 perovskite catalysts were prepared by citric acid sol-gel method,and then,LaCoO3 perovskite was etched with nitric acid.The structure,surface composition and reducibility of the catalyst were studied by X-ray diffraction (XRD),nitrogen desorption,transmission electron microscope (TEM),temperature program reduction of H2 (H2-TPR) and X-ray photoelectron spectroscopy (XPS).It was found that nitric acid etching did not change the crystal structure and the overall morphology of the LaCoO3 catalyst,but it can cause the exposure of B-site Co metal to the surface of the catalyst.As a result,after acid etching,the reducibility of the LaCoO3 catalyst was improved,leading to the improvement in the catalytic activity of the LaCoO3 catalyst for CO oxidation and C3H8 combustion.Moreover,the catalytic activity of the LaCoO3 catalyst after acid etching was higher than that of LaCo1.2O3 and CoOx/LaCoO3 catalyst.