Aqueous ammonia solution can be used to remove NO from waste gas streams by adding soluble cobalt(II) salt into aqueous ammonia solution. The hexamminecobalt(II) cations can not only bind nitric oxide but also activate oxygen molecules in aqueous solutions. Nitric oxide is absorbed and oxidized simultaneously in the same reactor. Nitric oxide can be turned into nitrite and nitrate. Activated carbon is used to catalyze the reduction of hexamminecobalt (III) to hexamminecobalt (II) to maintain the capability of removing NO with the hexamminecobalt solution. The influences of temperature and activated carbon particle size on the conversion of hexamminecobalt (III) are investigated. According to the experimental results, the catalytic reduction reaction rate increased with temperature. The influence of particle size of AC on the reduction of hexamminecobalt (III) in fixed bed reactor was very little. Oxygen in the gas phase was beneficial to the absorption of NO into the hexamminecobalt solution. The experiments performe manifestly that the hexamminecobalt solution coupled with catalytic regeneration of hexamminecobalt (II) was able to maintain a high nitric oxide removal efficiency for a long time. This method may have a bright promise in application.