Context: At the agro-ecosystem scale, a combination of green manure and chemical nitrogen fertilizer improves crop yield but also exacerbates soil CO2 emissions. However, it is unclear whether reducing nitrogen by reapplying green manure to fields can achieve high crop yields and improve carbon mitigation. Objective: This study aims to investigate the effects and underlying mechanisms of carbon emissions in maize fields under green manure reapplication combined with a reduction in nitrogen. Methods: A field experiment comprising five treatments (green manure reapplication combined with traditional nitrogen application (N100), green manure reapplication combined with a reduction in nitrogen of 10% (N90), green manure reapplication combined with a reduction in nitrogen of 20% (N80), green manure reapplication combined with a reduction in nitrogen of 30% (N70), and green manure reapplication combined with a reduction in nitrogen of 40% (N60)) was conducted at an arid oasis region in northwestern China from 2020 to 2022. This study investigated the effects of reducing nitrogen application while reapplying green manure to the field on maize grain yield, soil respiration rate, and carbon emission efficiency (CEE) and analyzed the relationship between soil respiration rate and soil temperature (Ts), soil water content (SWC), and crop biomass accumulation (BA). Results: The N80 treatment significantly reduced soil carbon emissions (CE) but did not reduce maize grain yield, and it showed a significant increase in CEE of 7.7% compared with the N100 treatment. In addition, this system can ensure no reduction in net primary production (NPP), net ecosystem production (NEP), and carbon sequestration (CS) potential compared with N100 and significantly improves the NPP/CE value. Soil temperature and crop biomass significantly correlated with soil respiration, which explained 68.4-72.9% and 84.4-88.8% of the seasonal variation of soil respiration, respectively. However, there was no correlation between soil moisture and soil respiration. Conclusion: Therefore, reducing nitrogen application by 20% while multiple cropping with green manure application after wheat was a suitable nitrogen fertilizer management measure for improving carbon mitigation in arid areas without sacrificing maize yield. Implications: The results of this study provide valuable insights into long-term agricultural management strategies for achieving high agricultural production and environmental friendliness.