Soil is one of the major sources for atmospheric N2O, NOX and NH3, especially for the agricultural soil with extensive management and high nitrogen fertilizer application. In this study, N2O, NOX and NH3 exchange fluxes from garlic field in the Yangtze Delta and maize-wheat rotation field in the North China Plain (NCP) were measured, and the influence factors were investigated. In addition, the mechanisms for N2O and NO emissions from maize-wheat field in the NCP were researched. The main results were obtained as following: (1) The domestic GC-ECD instrument was improved, and the instrument precision was increased from >1% to 0.31%. The method overcame the influence of CO2 concentration on N2O measurement. Good linear correlation (R2=0.9996) between the response of the improved ECD and N2O concentrations ensured the reliability of the single point correction method. (2) About 80% of N2O emission from the maize-wheat field in the NCP occurred after 10 days of the applications of the local fertilizer (compound fertilizer and urea), and the N2O emissions in the maize seasons accounted for 57%-86% of the total emissions of each year. Straw returning promoted obviously N2O emission in the long-term period. Large N2O yearly variations were found. We recognized that the soil temperature was a key influence factor for the N2O seasonal difference, and the inter-annual variations and the high N2O emissions from straw returning were ascribed to the soil moisture. (3) The current N-fertilizers used in the NCP could greatly promoted NO and NH3 emissions from the maize field, while straw returning to the field could greatly reduce NO and NH3 emissions. The high N2O seasonal emissions from the field probably had important contributions to the formations of regional photo oxidant O3 and fine particles. (4) We inferred that the N2O and NO emissions in the NCP were mainly from the nitrification during the short fertilization periods based on the molar ratio of NO/N2O, which was confirmed by the experiments of replacing ammonium with nitrate fertilizer and addition with the nitrification inhibitor (DCD). Replacing ammonium with nitrate fertilizer could decrease 54% and 100% of N2O and NO emissions from the whole maize-wheat season, respectively. (5) The simulated experiment of the agriculture soil in the NCP showed that the coupling mechanism of NO2- and NO3- could greatly promoted N2O emission. The soil incubation experiment indicated that NO2- could significantly inhibit the activity of N2O reductase. Therefore, we inferred that large amounts of NO2- and NO3- could be quickly produced after the application of ammonium fertilizer by nitrification, and the inhibition of NO2- formed to N2O reductase resulted in high N2O emission from the maize-wheat soil after ammonium fertilization.