The activities in NO + CO reaction of CuO-loaded TiO2/gamma-Al2O3 catalysts prepared by precipitation (P), co-precipitation (C-P), or sol-gel (S-G) were examined using a micro-reactor-gas chromatography (GC) system. The study showed higher catalytic activity of 12%CuO/15%TiO2/gamma-Al2O3 (P) than that of 12%CuO/15%TiO2/gamma-Al2O3 (S-G) or 12%CuO/15%TiO2/gamma-Al2O3 (C-P) in air condition, compared with higher activity of 12%CuO/15%TiO2/gamma-Al2O3 (P) or 12%CuO/15%TiO2/gamma-Al2O3 (S-G) than that of 12%CuO/15%TiO2/gamma-Al2O3 (C-P) in H-2 condition. The specific surface area and crystallite formation had little effect on catalytic activities. H-2-temperature programmed reduction (TPR) revealed four reduction peaks of 12%CuO/15%TiO2/gamma-Al2O3 (P), three reduction peaks of 12%CuO/15%TiO2/gamma-Al2O3 (S-G), but only one reduction peak of 12%CuO/15%TiO2/gamma-Al2O3 (C-P). CuO diffraction peaks were detected only in 12%CuO/15%TiO2/gamma-Al2O3 (P), indicating that CuO was highly dispersed on the other two TiO2/gamma-Al2O3 catalysts. As a result, 12%CuO/15%TiO2/gamma-Al2O3 (P) had the highest activity of reducing NO. During NO + CO reaction, the absorption peaks of intermediate product N2O were shown at 150 degrees C by 12%CuO/15%TiO2/gamma-Al2O3 (P), at 200 degrees C by 12%CuO/15%TiO2/gamma-Al2O3 (S-G), and at 100 degrees C by 12%CuO/15%TiO2/gamma-Al2O3 (C-P) after H-2 pretreatment at 400 degrees C for 1 h.