A laboratory incubation experiment was conducted to investigate nitrous oxide (N₂O) emission from an arable Ultisol as affected by antecedent water regime. The soil was maintained either air-dried (Sample D) or submerged (Sample S) for 110 days before the two soil samples were adjusted in soil moisture up to or down to 20%, 40%, 60%, 80% and 100% water holding capacity (WHC), respectively. And then they were incubated with or without 10% (v/v) acetylene for 138 h at 25℃. Results show N₂O emission from Sample S was 2.48 to 6.36 times as much as that from Sample D with soil moisture content ranging from 20% to 80% WHC (p <0.01). When the soil moisture content was adjusted to 100% WHC, N₂O emission from Sample S was only 19 percent of that from Sample D, and N₂O emission from Sample D incubated with acetylene was lower than that without acetylene (p <0.01). The content of nitrate increased after incubation with acetylene. CO₂ emission from Samples S and D increased with the soil moisture content. Heterotrophic nitrification might be present in the tested soil. Antecedent water regime significantly influences N₂O emission, and should hence be considered as a factor in determination of N₂O emission in situ.