Ammonia is a principal component of foul odors of agricultural and livestock wastes. This study investigated ammonia gas adsorption of rice husk carbonized in vacuum at different temperatures (300 ―800°C) for 3h. In an enclosed bag, 1.00 g of the carbonized rice husk was exposed to ammonia gas at 100 ppm. Rice husk carbonized at 400°C adsorbed ammonia the fastest. Its performance was much better than those of commercial deodorants. Pore characteristics and chemical characteristics of carbonized rice husk were examined to correlate them with the ammonia adsorption property. Remaining acidic functional groups were inferred to play a beneficial role in improving the ammonia adsorption.