Knowledge on nitrous oxide (N₂O) emissions from agricultural soils in semiarid regions is required for better understanding global terrestrial N₂O losses. Nitrous oxide fluxes from winter wheat fields in the semi-arid Loess Plateau of China were monitored using static chambers from 1 July 2007 to 30 June 2009 at biweekly intervals. After nitrogen fertilizer application, tillage, summer rainfall and during freezing and thawing cycles, additional measurements were conducted. There were two treatments, with or without winter wheat growing (referred to as WF_in and WF_ex, respectively). The results showed that there was no significant difference between two years for both treatments (P<0.05). The annual average N₂O emissions from WF_in and WF_ex were 2.05 kg · N₂O · hm^-2 · a^-1 and 2.28 kg · N₂O · hm^-2 · a^-1, respectively. The average emission factor for WF_in and WF_ex were 0.946% and 1.05%, respectively (uncorrected for background emission). The emission factor for WF_in was about one third (32.2%) lower than the default value provided by the Intergovernmental Panel on Climate Change for the application of synthetic fertilizers to cropland(1.25%). Therefore, the amount of N₂O emissions from the semiarid wheat field may be overestimated without using regional-specific factor. Seasonal variations in N₂O emissions were mainly affected by the short-time events including freeze and thaw cycles, nitrogen fertilizer application, tillage and summer rainfall. The greatest N₂O fluxes of WF_ex occurred during the freeze and thaw cycles of 2008 (February 29) with the value of 179.58 g · N₂O · m^-2 · h^-1. In comparison, the peak values of N₂O emission from WF_in occurred after tillage, fertilization and during continuous rainfall at the beginning of October, 2007, with the value of 93.4 g · N₂O · m^-2 · h^-1. There was significant correlation between N₂O fluxes from the WF_in and soil temperature (P<0.01), ambient air temperature (P<0.01) and water field pore space (WFPS) (P<0.05). The results of stepwise multiple linear regression showed that soil temperature and WFPS could be identified as the key factors determining the temporal variability of N₂O fluxes from the WF_in and accounted for 16.9% of the temporal variation. However, for the WF_ex treatment, N₂O fluxes were not correlated with any of these environmental and soil factors. Soil WFPS in the WF_in and the WF_ex was always below 60% except for during freeze-thaw in 2008and immediately after heavy rainfall, suggesting that nitrification was the important source of N₂O in this region.