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Field experiment was conducted in black soil paddy fields in Heilongjiang Province to explore the response regularity between NH3, N2O emissions and absorption of nitrogen fertilizer under water-saving irrigation and nitrogen fertilizer reduction in 2021. Two irrigation modes were set up: conventional flooding irrigation (F) and controlled irrigation (C). The nitrogen application rate throughout the entire growth period was set at three levels: conventional nitrogen application level (N, 110kg/hm2), nitrogen reduction 10% (N1, 99kg/hm2), and nitrogen reduction 20% (N2, 88kg/hm2). Under F and C irrigation modes, no nitrogen fertilizer treatment (CK1 and CK2) were set as the control, with a total of eight treatments. The effects of nitrogen fertilizer reduction on NH3 volatilization rate and N2O emissions fluxes during the entire growth period of rice under different irrigation modes were analyzed, the gaseous loss amount and gaseous loss rate of nitrogen fertilizer were calculated, and the absorption of nitrogen fertilizer by rice and the residual nitrogen fertilizer in the soil after rice harvest were further estimated based on isotope tracing technology. The results showed that the gaseous loss amount and gaseous loss rate of nitrogen fertilizer under both irrigation modes were decreased with the decrease of nitrogen application rate. The application of controlled irrigation mode increased the gaseous loss of nitrogen fertilizer in black soil paddy fields, and the gaseous loss amount and gaseous loss rate of each treatment were higher than those under conventional flooding irrigation mode with the same nitrogen application rate. However, isotope tracing results indicated that controlled irrigation mode can enhance absorption of nitrogen fertilizer by rice and effectively reduce nitrogen fertilizer loss. The absorption and recovery rate of nitrogen fertilizer by rice under controlled irrigation mode were significantly higher than those under conventional flooding mode with the same nitrogen application rate. Moreover, when the nitrogen application rate were the same, the loss amount and total loss rate of nitrogen fertilizer under controlled irrigation mode were significantly lower than those under conventional flooding mode (P<0.05). In total, nitrogen fertilizer reduction under controlled irrigation mode improved recovery rate of nitrogen fertilizer, reduced nitrogen fertilizer loss, and can stabilize or even increase rice yield to a certain extent. The research results can provide scientific basis for formulating water and fertilizer resource management strategies that were compatible with fertilizer conservation, efficiency enhancement, and emission reduction of paddy fields in Northeast China, which were of great significance for ensuring the sustainable development of agriculture in Northeast China.