Abstract: In this study, to provide a theoretical basis for the selection of slow-release nitrogen fertilizer application schemes in rice fields and for green and sustainable agricultural production, we sought to determine the optimal proportion of slow-release nitrogen fertilizer application and its effects on rice yield and greenhouse gas emissions. The effects of slow-release nitrogen fertilizer substitution for conventional nitrogen fertilizer and reduction of slow-release nitrogen fertilizer appllication on rice yield and greenhouse gases (CO₂, N₂O, and CH₄) emissions during rice cropping season were quantitatively assessed in paddy fields under straw return in the middle and lower reaches of the Yangtze River Basin. This study included the following six treatments: no fertilizer control (CK), conventional fertilization (CN), slow-release nitrogen fertilizer substitution for conventional nitrogen fertilizer based on the same nitrogen input (SRN), and 20%, 40%, and 60% nitrogen reductions (−20% SRN, −40% SRN, and −60% SRN) based on SRN. The results revealed that compared with the CK treatment, the highest rice yield (9.78 t∙hm⁻²) was obtained in plots receiving the SRN treatment, and that there were no significant differences between the −20% SRN and SRN treatments. Compared with CN treatment, the SRN and −20% SRN treatments were found to promote significant increases of 10.1% and 7.7% (P<0.05) in the rice yield, respectively, whereas the −60% SRN treatment contributed to a significant 11.2% reduction (P<0.05) in the rice yield. Furthermore, compared with the CK treatment, all the other fertilization treatments were found to promote significant increases in the cumulative emissions of CO₂, N₂O and CH₄, as well as in the global warming potential of paddy field soils, with a similar trend of CN ≈ SRN > −20% SRN > −40% SRN > −60% SRN > CK. In addition, compared with CK treatment, the CN, SRN, and nitrogen reduction treatments contributed to significant increases of 10.3%−34.0% (P<0.05) in greenhouse gas emission intensity; whereas compared with the CN treatment, SRN and nitrogen reduction treatments were found to be associated with significant reduction in greenhouse gas emission intensity ranging from 8.9% to 17.7% (P<0.05). Overall, our findings indicate that 20% is the optimal proportion of slow-release nitrogen fertilizer reduction applied in paddy field in this area. Adopting such practices could contribute to substantially enhancing soil fertility and rice yield, reduce greenhouse gas emissions, and promote sustainable agricultural development.