In order to investigate the effects of nitrogen fertilizer input on pepper yield，nitrogen use efficiency（NUE）and residual amount of mineral nitrogen（N_min）in soil，this study aimed to determine the critical plant nitrogen concentration and residual amount of N_min in root-zone soil，and make clear the optimal nitrogen application rate for pepper production in Southwest China. A field trial with pepper was conducted in Southwest China in 2023. Five treatments were set up：0 kg/hm² （N0），30% reduction of optimal nitrogen fertilizer rate（175 kg/hm² ，N175），optimal nitrogen application of 250 kg/hm² （N250），30% increase of optimal nitrogen fertilizer rate（325 kg/hm² ，N325）and farmer’s nitrogen application practice of 400 kg/hm² （N400）. The results showed that there was a linear-platform relationship between pepper yield and nitrogen application rate. There was no significant difference in pepper yield，above-ground dry matter and nitrogen accumulation in the N250 treatment，compared to the N400 treatment. However，the proportion of dry matter distribution and nitrogen distribution in pepper fruit were significantly increased by 10.3% and 9.6%，respectively. Nitrogen recovery efficiency， nitrogen agronomic efficiency and nitrogen partial productivity were significantly increased by 45.0%，55.1% and 56.1%， respectively. In addition，there was a linear-plateau relationship between above-ground dry matter accumulation of pepper and above-ground plant nitrogen concentration as well as N_min residue in root-zone soil. The above-ground critical plant nitrogen concentrations required for maximum upper dry matter accumulation at flowering and fruit-setting stage，middle-fruiting stage，peak-bearing stage and end fruiting stage of pepper were 30.0，26.3，24.2 and 26.5 g/kg，respectively. The residual N_min in critical root layer soil was 77.7，67.2，56.9 and 48.2 kg/hm² ，respectively. The study showed that the application rate of 250 kg/hm² could ensure the appropriate root-zone soil N_min and plant nitrogen concentration，maintain high pepper yield， increase the ratio of nitrogen and dry matter distribution in pepper fruits，and significantly improve nitrogen use efficiency. The results are of great significance in guiding the vegetable production in Southwest China.