Abstract: To reveal the roles of reactive oxygen metabolism in drought-resistance improvement by fulvic acid potassium in flue-cured tobacco seedlings, the effects of fulvic acid potassium (foliar spraying) on ROS, autioxidant enzyme activities, antioxidant content and MDA content in leaves of flue-cured tobacco with different drought resistance, drought resistant cultivar (honghuadajinyuan) and drought sensitive cultivar (yunyan100) grown under drought stress were investigated by hydroponic experiments. The results showed that the O₂^- production rate, H₂O₂ and MDA contents in leaves of flue-cured tobacco seedlings were increased, the activities of SOD, POD and CAT were all significantly enhanced under drought stress, and the content of GSH was significantly increased during the initial period of drought stress, however, the content of AsA was decreased. Under stress conditions, foliar spraying of fulvic acid potassium could effectively enhance the activities of antioxidase and the amount of antioxidants, and decrease the content of superoxide anion, hydrogen peroxide and MDA. Compared with Honghuadajinyuan, there was greater influence on Yunyan100 under drought stress, and fulvic acid potassium could effectively alleviate the stress-induced damage to Yunyan100. These results indicated that fulvic acid potassium could alleviate stress-induced damage to flue-cured tobacco seedlings and improve its drought tolerance through increasing of antioxidants activities/contents.