Abstract: A series of coal activated carbon supported metallic oxide were preparedby incipient-wetness impregnation method with cuprammonium complex and so on.The pore structure, metal distribution and morphology of activated carbon before and after loading of metal sites were analyzed by N₂ adsorption-desorption, scanning electron microscope, energy dispersive spectroscopy and transmission electron microscope.The HCN defence time of carbon catalyst was also tested. Hence, the effect of pore size distribution of activated carbon supportor on the HCN defence performance of catalyst was demonstrated.The effective pore size distribution of activated carbon for adsorbing cuprammonium complex was 1.2-2.1 nm, which facilitated the penetration of cuprammonium complex inside the carbon supportor and formation of the active sites for dispersing Cu₂O and enhancement of HCN defence time. However, the mesopores(>2.1 nm) of carbon supportor would result in the severe accumulation of the active particles, reduction of metal dispersion and thus decreasing the HCN defence performance of carbon catalysts.The HCN defence time of activated carbon supported catalyst was longer than 30 min, as the pore volume of activated carbon with the pore size of 1.2-2.1 nm was over 0.142 4 cm³/g and the pore volume with the pore size of >2.1 nm was less than 0.082 4 cm³/g.