The copper based catalysts, CuO/gamma-Al2O3, CuO/gamma-Al2O3-cordierite (Cord) and CuO/Cord, were prepared by impregnation method. The catalytic activity of the catalysts was tested in absence and presence of water vapor, and the catalysts were characterized. Temperature program desorption (TPD) experiments of toluene and water on the catalysts were carried out. The influence of water vapor on the activity of the catalysts was discussed. Results showed that addition of the water vapor has a significant negative effect on the catalytic activity of the catalysts. The higher the concentration of the water vapor in feed steam was, the lower the catalytic activity of the copper based catalysts became, which could be mainly ascribed to the competition of water molecules with toluene molecules for adsorption on the catalyst surfaces. TPD experiments showed that the strength of the interaction between water molecules and three catalysts followed the order: CuO/gamma-Al2O3>CuO/gamma-Al2O3-Cord>CuO/Cord. As a consequence of that, the degree of degradation in the catalytic activity of these three catalysts by the water vapor followed the order: CuO/gamma-Al2O3>CuO/gamma-Al2O3-Cord>CuO/Cord. However, the negative effect of the water vapor was reversible.