Abstract: To explore the long-term effects of different proportions of organic carbon input on nitrogen supply capacity of tobacco-growing soil under chemical fertilizer reduction, four treatments were set up based on 11 consecutive years of field experiments: no fertilizer (CK), local conventional recommended fertilizer (100% chemical fertilizer, CF), 20% reduction of chemical fertilizer with 3 000 kg·hm⁻² organic fertilizer (OF-1), and 40% reduction of chemical fertilizer with 6 000 kg·hm⁻² organic fertilizer (OF-2). The effects of different proportions of organic carbon input on the soil nitrogen pool activity of tobacco-growing soil under continuous chemical fertilizer reduction were investigated by analyzing and comparing the content of soluble nitrogen components, soil nitrogen pool activity, soil nitrogen pool management index, tobacco yield, and economic traits. The results showed that no fertilizer (CK) treatment significantly reduced the tobacco yield, proportion of medium-quality and high-quality tobacco leaves, soil soluble nitrogen fraction content, and nitrogen pool management index. Under continuous chemical fertilizer reduction conditions, different proportions of organic carbon input (OF-1 and OF-2) significantly increased tobacco yield, soil soluble nitrogen content, soil nitrogen pool activity, and the nitrogen pool management index. Compared to the CF treatment, the OF-1 and OF-2 treatments with different organic carbon input ratios significantly increased the content of total soluble nitrogen in tobacco-growing soil, by 52.11% and 57.36%, respectively; the soluble organic nitrogen content significantly increased by 99.25% and 102.64%, respectively; the ammonium nitrogen content significantly increased by 18.08% and 19.22%, respectively; the nitrate nitrogen content significantly increased by 48.09% and 54.61%, respectively; the soil nitrogen pool activity significantly improved by 53.58% and 50.36%, respectively; soil nitrogen pool management index significantly increased by 48.21% and 50.57%, respectively; tobacco leaf yield also showed significant improvements, increasing by 18.69% and 19.22%, respectively; the proportion of prime-quality tobacco leaves increased by 94.95% and 67.61%, respectively, whereas the proportion of medium-quality and high-quality tobacco leaves increased by 13.91% and 12.25%, respectively. The effects of the OF-1 and OF-2 treatments on soil nitrogen pool activity and the nitrogen pool management index were not significantly different. The results of the correlation analysis showed that nitrogen composition, soil nitrogen pool activity, and nitrogen pool management index of tobacco-growing soil were significantly positively correlated with tobacco yield and economic traits. Random forest analysis showed that the soil nitrogen pool management index, soil soluble nitrogen content, and soil nitrogen pool activity were important predictors of changes in tobacco yield. In conclusion, under continuous chemical fertilizer reduction, organic carbon input enhanced tobacco leaf yield by increasing soil soluble nitrogen content and improving soil nitrogen pool activity and the nitrogen pool management index. This approach serves as a green and ecological fertilization strategy to achieve chemical fertilizer reduction and improved efficiency. It also enhances the soil nitrogen supply capacity and promotes high-quality tobacco production.