Lettuce seeds (Lactuca sativa L.),the common allelopathy bioassay system,were germinated in the presence of decomposition of terminal bud and axillary bud of flue-cured tobacco K326 for evaluating its allelopathic potential. Results showed that seed germination of lettuce could be promoted by low concentrations,however, inhibited by high concentrations of decomposing tobacco, and the concentration by 0.10 g/mL has the most significant inhibition. Decomposing tobacco residues also had a similar effect on seedling growth of lettuce that was performed on seed germination. Low concentration by 0.05 g/mL has some inhibitive effect and high concentrative by 0.10 g/mL has the most significant inhibitive effect on seedling growth. In conclusion, significant inhibitory effect on seed germination and seedling growth could be formed in process of tobacco residues’ decomposing .