Abstract: Clarifying the nitrogen (N) flow characteristics of the crop-livestock system in Henan Province under the action of fertilizer reduction and efficiency increase was important for quantification of the chemical N fertilizer reduction and N use efficiency increase potential, which can provide the theoretical support for regional agriculture green development. We collected the research date from statistical yearbooks and literatures, and used NUFER (NUtrient flows in Food chains, Environment and Resources use) model to analysis the N flow characteristics of crop-livestock system in Henan Province in 2010 (rapid increase of N fertilizer usage), 2015 (peak of N fertilizer usage) and 2022 (decrease of N fertilizer usage). N use efficiency and environmental loss were quantified. Moreover, the potential of chemical N fertilizer reduction and efficiency increase was determined through scenario analysis. The total N input in the crop-livestock system in 2010, 2015 and 2022 increased first and then decreased in Henan Province, which were 321.2, 337.4 and 2.637 ×10⁴ t, respectively. Compared with 2015, the N input in 2022 decreased by 19.8%. Fertilizer input was the largest input path in each year, and soil accumulation and ammonia volatilization loss were the largest two output paths excepted the main animal and crop products. The N use efficiency of cropping system and crop-livestock system increased in 2010, 2015 and 2022. However, the N use efficiency of livestock system changed little in the three years. The total environmental loss in 2010, 2015 and 2022 increased first and then decreased, accounting for 45.8%−46.4% of the total N input. Compared with 2015, the N use efficiency of cropping, livestock and crop-livestock system in 2022 increased by 9.9, 0.2 and 8.5 percentage points, respectively, and the environmental loss of crop-livestock system decreased by 19.2%, and the N cycling rate increased by 0.9 percentage points, and the food N cost decreased by 22.9%. Scenario analysis showed that the crop-livestock system in Henan Province could further reduce N fertilizer use by 33.0%, 38.4% and 37.3%, and decrease environmental loss by 20.7%, 28.5% and 36.6%, and increase N use efficiency by 10.5, 12.8 and 12.4 percentage points, respectively, through three progressive measures of reducing chemical fertilizer, increasing the proportion of manure returning to the field and optimizing animal feed structure. There still has a great potential for fertilizer reduction and efficiency increase in the crop-livestock system. The national action of fertilizer reduction and efficiency increase had achieved remarkable effects in Henan Province, which provided an important role for supporting the agriculture green development. In addition, there still exists a great potential for fertilizer reduction, efficiency increase in the future.