[Objectives] The effects of different irrigation treatments on gaseous nitrogen loss and nitrogen cycle functional genes in a greenhouse cucumber ecosystem were explored to provide data support for further studies on gaseous nitrogen loss in a greenhouse farmland system under different irrigation methods. The results provide a theoretical basis for the formulation of irrigation schemes in greenhouse vegetable production systems in China. [Methods] Facility cucumbers were chosen as the research subjects for field experiments. The experimental designs included traditional irrigation (100% IWD), 25% water-saving irrigation (75% IWD), and 50% water-saving irrigation (50% IWD). Through in situ field monitoring experiments, continuous observations and records of N₂O emissions and ammonia volatilization from the soil of facility cucumbers were made using static chamber-gas chromatography and ventilation absorption. Nitrogen cycle functional genes were identified using high-throughput qPCR gene chip technology. [Results] ① Among the various irrigation treatments, the cumulative emissions of N₂O were as follows: 100% IWD > 75% IWD (p<0.05) and 100% IWD > 50% IWD (p<0.05). ② Cumulative ammonia volatilization was 75% IWD > 50% IWD > 100% IWD (p<0.05). ③ The overall abundance of nitrogen cycle functional genes in the soil changed significantly (PERMANOVA, F=241.82, p=0.001). ④ Cucumber yield was 100% IWD > 75% IWD > 50% IWD (p<0.05). [Conclusion] Irrigation at 50% significantly increased nitrification gene abundance, whereas 75% and 50% irrigation significantly decreased denitrification gene abundance. Denitrification was the main factor affecting N₂O gas production in surface soil treated with 100% irrigation. Reducing the irrigation water volume by 25% led to a decrease in denitrification gene abundance in the surface soil and weakened the denitrification process in the surface soil, reducing N₂O emissions. However, reducing irrigation water by 50% did not significantly change denitrification gene abundance or N₂O emissions at the soil surface.