Ag-promoted Co-ZSM-5 catalyst was prepared and tested for the selective catalytic reduction of NO with methane. The low-temperature activity and water-resistant ability of the promoted catalyst were markedly improved in comparison to Co-ZSM-5. The NO conversion was about 100% in the temperature range of 350-550 degrees C at a space velocity of 6,000 h(-1) and nearly 60% in the presence of 2% water steam. The results showed that with Ag presence, the redox nature of cobalt species changed. The improvement of low-temperature activity and water-resistance of catalyst is attributed to the suppression of methane combustion and the formation of surface nitrate species.