Abstract: To clarify the effect of nitrogen fertilizer topdressing ratio on nitrogen uptake, utilization, chemical components and sensor quality of flue-cured tobacco, a field experiment of different basal-topdressing ratios was conducted on cultivar‘NC55’by using 15N tracer technique. The results showed that improving the topdressing ratio decreased the basal fertilizer nitrogen uptake amount of different organs and total plant, but increased the topdressing fertilizer nitrogen amount. The treatment with 50% nitrogen topdressing had the highest fertilizer nitrogen uptake amount. With the improving of topdressing ratio, the soil nitrogen uptake amount increased firstly, and then reduced. The soil nitrogen uptake amount of stem, leaf and total plant decreased significantly when the topdressing ratio exceeded 30%. With the improving of topdressing ratio, the basal fertilizer-N use efficiency increased, but that of topdressing decreased, and the whole fertilizer-N use efficiency increased firstly, then reduced, and the highest fertilizer-N use efficiency was achieved with 50% nitrogen topdressing. The leaf sensory quality improved with the increasing of topdressing ratio until up to 50%, and it became worse if the ratio exceeded 50%. Under the field fertility of this experiment, 50% nitrogen top dressed was the optimal treatment taking account of nitrogen utilization and quality. The finding provided a scientific basis for rational application of nitrogen fertilizer of flue-cured tobacco.