Abstract: Clarifying the nitrogen (N) flow characteristics of the crop-livestock system in Henan Province under fertilizer reduction and efficiency increase is important for quantifying the chemical N fertilizer reduction and N use efficiency increase potential. This can provide theoretical support for regional agricultural green development. We collected research data from statistical yearbooks and literature and used the NUtrient flows in Food chains, Environment and Resources use (NUFER) model to analyze the N flow characteristics of crop-livestock system in Henan Province in 2010 (rapid increase in N fertilizer usage), 2015 (peak of N fertilizer usage), and 2022 (decrease in N fertilizer usage). The N use efficiency and environmental losses were quantified. Moreover, the potentials for chemical N fertilizer reduction and efficiency increases were determined through scenario analysis. The total fertilizer N input in the crop-livestock system in 2010, 2015, and 2022 first increased and then decreased in Henan Province at 321.2×10⁴, 337.4×10⁴, and 263.7×10⁴ t, respectively. Compared with 2015, the fertilizer N input in 2022 decreased by 21.8%. Fertilizer N input was the largest input item, and soil accumulation and ammonia volatilization loss were the two largest output items, except for the main animal and crop products. The N use efficiency of cropping and crop-livestock systems increased from 2010 to 2022. However, the N use efficiency of the livestock system changed little over this period. The total N environmental loss in 2010, 2015, and 2022 increased first and then decreased, accounting for 45.8%−46.4% of the total N input. Compared to 2015, the N use efficiency of cropping, livestock, and crop-livestock systems in 2022 increased by 9.9%, 0.2%, and 8.5% (absolute change), respectively; the N environmental loss of the crop-livestock system decreased by 19.2%; the N recycle rate increased by 0.9% (absolute change); and the N cost of food decreased by 22.9%. Scenario analysis showed that the crop-livestock system in Henan Province could further reduced N fertilizer use by 33.0%, 38.4%, and 37.3%, decreased N environmental loss by 20.7%, 28.5%, and 36.6%, and increased N use efficiency of crop-livestock system by 10.5%, 12.8%, and 15.5% (absolute change), respectively, through three progressive measures: reducing chemical fertilizer, increasing the proportion of manure returned to the field, and optimizing animal feed structure. There is still great potential for fertilizer reduction and efficiency increases in crop-livestock systems. Fertilizer reduction and efficiency increase achieved remarkable effects in Henan Province, which played an important role in supporting green agricultural development.