Nitrogen fertilizer is essential for food security, but its excessive application leads to reactive nitrogen emissions, causing severe environmental issues. In the new era of promoting green development, clarifying China's reasonable nitrogen fertilizer demand and pathways for reducing chemical nitrogen fertilizer is crucial for agricultural transformation and upgrading. This study comprehensively analyzes the yield potential and nitrogen demand of 31 major crops in China and determines the reasonable nitrogen fertilizer demand under the conditions of food security and ecological sustainability by combining the nitrogen surplus levels under optimized management for different crops. Under the green development framework, the total reasonable nitrogen nutrient demand in China is 31 million tons, with a reasonable chemical nitrogen fertilizer demand of 19.04 million tons, accounting for 61% of the total demand. Future pathways for rational nitrogen fertilizer application in China should consider nitrogen fertilizer quota, increasing organic nutrient input and substitution ratio, increasing the planting proportion of leguminous crops to enhance biological nitrogen fixation potential, and optimizing nitrogen fertilizer product structure. Under these pathways, the potential for reducing chemical nitrogen fertilizer ranges from 26% to 53%. Specifically, under reasonable nitrogen input conditions (nitrogen quota), increasing the organic nutrient substitution ratio to 40% could lower the chemical nitrogen fertilizer demand to 14.28 million tons, with a reduction potential of 44%. Further increasing the planting area of leguminous crops (enhancing soybean-maize rotation ratio) could reduce the chemical nitrogen fertilizer demand to 13.6 million tons, with a reduction potential of 47%. Finally, optimizing the nitrogen fertilizer product structure could further reduce the reasonable chemical nitrogen fertilizer demand to 12.13 million tons, with a reduction potential of 53%. This study's evaluation of reasonable nitrogen fertilizer demand and exploration of green development pathways for nitrogen fertilizer will aid in implementing more scientific management systems and provide scientific support for the upgrading of China's nitrogen fertilizer industry.