Abstract: In order to investigate the effects of root exudates on continuous tobacco cropping problem, three varieties of tobacco (Zhongyan100, NC89, K326) were used to identify the root exudates in different extracting conditions, and the effects of root exudates of Zhongyan 100 in different extracting conditions on tobacco seed. The results show that, the root exudates in different extracting conditions of the three varieties mainly contained organic acids. Under neutral condition, the components of root exudates included 2-hydroxyl propionic acid, Tetradecanoic acid, Neophytadiene, Scopoletin and Octanoic acid. Under acid condition, the components of root exudates included 3-hydroxy butyrate, Neophytadiene, Succinic acid, Hexadecanoic acid and Cinnamic acid. Under alkaline condition, the components of root exudates included Neophytadiene, Hexadecanoic acid and Stearic acid. 2-hydroxyl propionic acid, Benzoic acid, Succinic acid, Nicotine,Neophytadiene, Tetradecanoic acid, Hexadecanoic acid and Fumaric acid were identified in the root exudates of all the three varieties of tobacco. The grade of influence by root exudates of Zhongyan 100 in different extracting conditions on tobacco seed were (from high to low): neutral condition, alkaline condition and acid condition. Fumaric acid, Succinic acid and Nicotine had certain inhibition on the germination rate of the tobacco seeds. The germinating percentage of tobacco seed decreased with increasing dosage of these three compounds.