A series of CuO/Al2O3 catalysts for CO oxidation were prepared by impregnation method with different loadings. CuO species and solid-solid interaction in CuO/Al2O3 catalysts were characterized by high-temperature in situ XRD, Raman spectroscopy and H-2-TPR techniques. CuAl2O4 is formed as a result of solid-solid interaction between CuO and Al2O3 when the calcination temperature reached 700 degrees C. Combine with XRD and Raman results, it is found that CuO species is on the surface region of CuO/Al2O3 catalysts, while CuAl2O4` is in the internal layer of CuO. The formation of CuAl2O4 inhibits CuO diffusing into Al2O3 support, which indicates that CuO can stabilize on the surface region of the catalysts at high temperatures. There are three H-2-TPR peaks namely, alpha(1), alpha(2) and beta, which are attributed to the highly dispersed CuO species, bulk CuO species, and spinel CuAl2O4, respectively. The activity of CuO/Al2O3 catalysts for CO oxidation increased with increasing CuO loading. However, the increase of calcination temperature from 400 to 900 degrees C resulted in a decrease of the activity in CO oxidation. Combine with H2-TPR and CO oxidation activity, it is supposed that the catalytic activity is related to both the highly dispersed CuO and bulk CuO. (c) 2005 Elsevier B.V. All rights reserved.