With static-closed-chamber and GC (Agilent 4890), the nitrous oxide (N2O) flux in spring wheat field ecosystem in the Sanjiang Plain of Northeast China was continuously observed in situ from May 2004 to October 2006. The results showed that the N2O flux presented obvious seasonal and inter-annual variation, which was mainly related with precipitation and field water management. The diurnal variation of N2O flux had correlations with the air temperature and the temperature at 5 cm underground. Wheat field ecosystem was the strong sources of atmosphere N2O during plant growth season. The N2O flux decreased obviously in fallowing period, was weaker in freezing period, and increased slowly when soil thawing. The average N2O flux in wheat growth season was 0.190 mg x m(-2) x h(-1), the flux was 0.077 mg x m(-2) x h(-1) from after-reaping to before-freezing period, and 0.017 mg x m(-2) x h(-1) in freezing and thawing period.