Abstract: To study the effects of Exobasidium japonicum liquid culture on growth and key enzymes of carbon and nitrogen metabolism of flue-cured tobacco seedlings, with K326 as the test material, different concentrations (original solution, 1/10 original solution, 1/50 original solution and 1/100 original solution) of the liquid culture were used to spray the flue-cured tobacco seedlings, the effects on growth, chlorophyll content, root activity and key enzyme activities of carbon and nitrogen metabolism of flue-cured tobacco seedlings were analyzed. The results showed that on the third day after treatment, the root activity of seedlings treated with 1/50 original solution was the highest, which was 276 μg/(g·h) higher than that of CK. Chlorophyll a content, chlorophyll b content and carotenoid content were increased by 0.324, 0.104 and 0.060 mg/g respectively. On the 7th day after treatment, the activities of NR, GS, SSS, SPS and INV of seedlings treated with 1/100 original solution were the highest, which were significantly increased by 0.36, 0.44, 5.16, 58.02 and 362.60 U/g compared with the control. On the 11th day after treatment, leaf length, leaf width, leaf area and plant height of seedlings treated by 1/100 solution were significantly higher than those treated by CK, increased by 3.11 cm, 1.03 cm, 25.39 cm² and 5.13 cm, respectively. Different concentrations of E. japonicum liquid culture had different effects on tobacco seedlings. In summary, 1/100 original solution concentration promoted the growth of flue-cured tobacco seedlings with the most significant effect, followed by 1/50 original solution.