Boron is essential for tobacco growth. The effect of boron on the carbohydrate and nitrogen metabolism was investigated by cultural technology in the greenhouse. Flue-cured tobacco ( Nicotiana tabacum L.) variety K326 was used as experimental materials. The experimental seedlings were produced by float system. Vermiculite/pearlite (V:V=1:1) culture was used for the seedlings, and every day the seedlings were sprayed with Hoagland or Aron culture solutions containing 5 µmol or 20 µmol or 40 µmol H₃BO₃ respectively. 60 days after culturing the tobacco plants were collected and analyzed for the dry weight of root, stem and leaves. Boron, nitrogen, nitrate-nitrogen (NO₃-N), ammonium-nitrogen (NH₄-N) and potassium contents were tested. The research results showed that boron deficiency (5 µmol H₃BO₃) can significantly decrease the accumulation of boron, nitrogen, potassium and dry matter in tobacco plant organs. Meanwhile boron deficiency (5 µmol H₃BO₃) affected the ability of tobacco plant absorption and assimilation to NO_3-, inhibited nitrogen metabolism, increased NH₄₊ content and decreased amino acid and protein in the leaves. The boron-deficient tobacco plants had lower photosynthetic rates, more sugars, such as glucose, fructose, sucrose and starch than healthy ones. As the supply of boron increased (20 µmol H₃BO₃) the tobacco plant ability of both carbohydrate metabolism and accumulation of dry matter was enhanced, the contents of nitrogen, potassium and boron increased.