Abstract: According to the analysis of N₂0 production mechanism and its controlling factors in soil,the accumulation of organic carbon and nitrate during a dry season fallow,the occurrence of sudden,the strong N₂0 emission pulses,and the distribution area of global paddy fields,it suggests that the paddy fields following a dry season fallow might be a potential important N₂0 source in the tropical and sub－tropical regions.The glogal annual N₂0 emission(calculated by N₂0—N)from this source is estimated about 0.75 Tg.