The effect of high-temperature pretreatment in the presence of steam on NO conversion of protonated cobalt-incorporated silicate having MFI structure (H-Co-silicate) and copper-ion-exchanged MFI-type zeolite (Cu/H-ZSM-5) was studied. The activity of Cu/H-ZSM-5 decreased with an increase of pretreatment temperature. In contrast with Cu/H-ZSM-5, the activity of H-Co-silicate for NO removal increased with the pretreatment temperature. As for H-Co-silicate, the pretreatment at 1000(degrees)C was the optimum condition to enhance the conversion that was four times higher than that without pretreatment. The destruction of framework and loss of cobalt species were not observed after the pretreatment. Some parts of cobalt species migrated from the framework and became active sites that enhance the activity for NO removal.