Biochar amendment to agricultural soil is regarded as a promising option to mitigateclimate change and enhance soil quality. It could sequester more carbon within the soil systemand increase plant yield by changing soil physicochemical characteristics. However, sustainableuse of biochar requires comprehensive environmental assessment. In this sense, it is important tomeasure additional greenhouse gas emission from soils after biochar addition. We investigatedemissions of CO2, N2O, and CH4from incubated soils collected from rice paddy and cultivatedgrassland after amendment of 3% biochar(wt.) produced from rice chaff. During incubation,soils were exposed to three wet-dry cycles ranging from 5~~85% soil gravimetric water content(WC) to investigate the changes in effect of biochar when influenced by different water levels. TheCO2emission was reduced in biochar treatment compared to the control at WC of 30~~70% bothin rice paddy and grassland soils. This indicates that biochar could function as a stabilizer for soilorganic carbon and it can be effective in carbon sequestration. The N2O emission was alsoreduced from the grassland soil treated with biochar when WC was greater than 30% because thebiochar treated soils had lower denitrification due to better aeration. In the rice paddy soil,biochar addition resulted in decrease in N2O emission when WC was greater than 70%, while anincrease was noted when WC was between 30~~70%. This increase might be related to the factthat available nutrients on biochar surface stimulated existing nitrifying bacterial community,resulting in higher N2O emission. Overall results imply that biochar amendment to agriculturalsoil can stabilize soil carbon from fast decomposition although attention should be paid toadditional N2O emission when biochar addition is combined with the application of nitrogenfertilizer.