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In order to explore the effects of different water and nitrogen management modes on carbon fixation and carbon emission reduction in black soil paddy fields, a field experiment was conducted. Two irrigation modes of conventional flooding irrigation (F) and controlled irrigation (C) were set up, and three nitrogen application rates of 110kg/hm2(N), 99kg/hm2(N1,10% nitrogen reduction) and 88kg/hm2 (N2,20% nitrogen reduction) were selected. The CO2 emission intensity and CH4 emission intensity of rice soil respiration under six water and nitrogen management modes were measured, and the dry matter quality, carbon content and carbon sequestration of each organ after rice harvest were calculated. The results showed that under different water and nitrogen management modes, the soil respiration CO2 emission intensity of each treatment showed a single peak change, and reached the peak at the tillering stage. The methane emission of each treatment showed a double peak change and reached the peak at the tillering stage and the two time periods after the application of panicle fertilizer. Under the same irrigation method, with the decrease of nitrogen application rate, soil respiration CO2 emission intensity and methane emission intensity were also decreased significantly (P<0.05). Under the same nitrogen application rate, compared with conventional flooding irrigation, controlled irrigation effectively reduced methane emission intensity, but increased soil respiration CO2 emission intensity. Under different water and nitrogen management modes, the total carbon sequestration after rice harvest was 319.37~489.00g/m2. The carbon sequestration of each organ after rice harvest from small to large was leaf, root, stem and spike, which were 5.16%~6.72%, 5.71%~10.78%, 28.62%~36.66% and 49.53%~58.70% of the total carbon sequestration of the plant, respectively. Compared with conventional flooding irrigation, controlled irrigation effectively improved the carbon sequestration capacity of plants. Under different water and nitrogen management modes, the net primary productivity (NPP) and gross primary productivity (GPP) of rice reached the highest in the treatment of 10% nitrogen reduction. Under the same irrigation method, with the increase of nitrogen application rate, the trend showed increase first and then decrease; at the same nitrogen application rate, NPP and GPP under controlled irrigation were higher than those under conventional flooding irrigation. Controlled irrigation had higher production potential than conventional flooding irrigation. Except that the net soil carbon budget of CN treatment was negative, the other treatments were positive, that was, except for CN treatment, the other treatments showed the effect of net soil carbon gain. At the same nitrogen application rate, the net soil carbon gain under conventional flooding irrigation was higher than that under controlled irrigation, but the difference was not significant (P>0.05). With the decrease of nitrogen application rate, the soil carbon budget of each treatment was increased first and then decreased under the same irrigation system. Considering comprehensively, CN1 treatment can improve soil carbon sequestration capacity and reduce soil carbon loss and greenhouse gas emissions from paddy fields under high production capacity.