Agricultural soil has become the largest anthropogenic source of atmospheric nitrous oxide (N₂O). To estimate the impacts of longterm combined application of organic and inorganic fertilizers on N₂O emission in a typical winter wheatoil sunflower cropping system in the Ningxia irrigation area, we measured N₂O fluxes using the static opaque chambergas chromatograph method and monitored the seasonal dynamics of related factors. Our results showed that nitrogen addition in the previous crop field significantly stimulated N₂O emissions during the following oil-sunflower cultivation, and the mean fluxes of N₃₀₀-OM, N₂₄₀-OM_1/2, N₃₀₀ and N₂₄₀ were (34.16+9.72), (39.69+10.70), (27.75+9.57) and (26.30+8.52) μg·m^-2·h^-1, respectively, which were 4.09, 4.75, 3.32 and 3.15 times of the control groups. The total cumulative N₂O emissions of fertilizer treatments in growing season was as high as  796.7 to 1242.5 g·hm^-2, which was  2.99 to 4.67 times of the control groups. During the growing season, the rates of N₂O emission in each month organic and inorganic fertilizers combined treatments were similar at high levels. N₂O emission in chemical fertilizer treatments gradually decreased, and the main period of N₂O emission occurred at the beginning of growing season. Taking July for example, N₂O emission accounted for 41.3% to 418% of total cumulative amount. The amounts of N₂O emission under organic and inorganic fertilizers
 combined treatments were significantly higher than under chemical fertilizer treatments. The N₂O emissions were not significantly different between conventional and optimized applications of nitrogen fertilizer under the same fertilizing method, either between N₃₀₀-OM and N₂₄₀-OM_1/2, or between N₃₀₀ and N₂₄₀. On account of the drought, N₂O emission in each treatment was mainly affected by soil moisture. N₂O emission had a significant positive correlation with soil ammonium nitrogen content under combined applications of organic and inorganic fertilizers, but was not correlated with soil nitrate nitrogen content under all treatments. This showed that adding organic fertilizer could stimulate the N₂O production via increasing the soil ammonium nitrogen content.