Abstract: To investigate the nitrogen utilization characteristics of different tobacco types and varieties and establish the reasons behind different nitrogen utilization efficiency, experiments using two tobacco cultivars, Hongda (flue-cured tobacco) and TN86 (burley tobacco) of different nitrogen efficiencies were carried out in a floating system. The activities of key enzymes involving nitrogen metabolism, pigment content, nitrogen accumulation and biomass of seedlings of the two cultivars were determined. The results showed that:1) The seedlings of flue-cured tobacco cv. Hongda had a higher biomass, glutamine synthetase (GS) activity and pigment content, a stronger nitrogen assimilating capacity, a larger nitrogen accumulation amount and great nitrogen utilization efficiency. 2) The seedlings of burley tobacco cv. TN86 had a lower biomass, glutamine synthetase activity and pigment content, a higher nitrate reductase (NR) activity, a stronger nitrate reduction capacity, a weaker nitrogen assimilating capacity, a higher total nitrogen content, a low nitrogen accumulation amount and nitrogen utilization efficiency. The correlation analysis suggested that glutamine synthetase activity, nitrate reductase activity and pigment content closely correlated to nitrogen accumulation and utilization efficiency, especially the correlation of glutamine synthetase activity and chlorophyll content with nitrogen accumulation and utilization efficiency. Therefore, promoting pigment contents and the nitrogen assimilation activity could be used as an approach for cultivation technology and genetic variety improvement.