The study aimed to clarify the influence of nitrogen application rate on the growth and carbon-nitrogen metabolism of upper tobacco leaves within 30 days after topping，and to explore the relationship between different nitrogen application rate with the economic trait indicators of upper tobacco leaves. Yunyan 87 was used as the material，and nitrogen application rate treatments of 90.0，112.5，135.0，157.5，and 180.00 kg/hm² were set up. The leaf length，width，dry matter mass，SPAD value，activities of nitrate reductase and α-amylase，total nitrogen and starch contents of the upper six tobacco leaves in different treatments were measured at the time of topping and 10，20，and 30 d after topping，as well as the economic traits of the upper tobacco leaves. The results showed that with the increase of nitrogen application rate，the length，width，dry matter mass，SPAD value，activities of nitrate reductase and α-amylase，total nitrogen and starch contents of the upper tobacco leaves increased. Thirty days after topping of flue-cured tobacco，the upper leaves were still growing and accumulating dry matter，and their increment increased with the increase of leaf position，while the growth rate gradually slowed down. The SPAD value，nitrate reductase activity，total nitrogen and starch contents of the leaves first increased and then decreased after topping of flue-cured tobacco. The decrease occurred relatively later in the leaves at higher positions and earlier in the leaves at lower positions. The activity of α-amylase first decreased and then increased after topping of flue-cured tobacco. The increase occurred relatively later in the leaves at higher positions and earlier in the leaves at lower positions. The relationship between the nitrogen application rate and the proportion of high-grade tobacco leaves was linear，while the relationships with the average price，yield，and output value were quadratic parabolic. When the nitrogen application rate was 148.50-158.49 kg/hm²，both the yield and output value of tobacco leaves were relatively ideal.