Abstract: In order to compare the response of different organs of flue-cured tobacco seedling to low or high temperature stress, the relative conductivity of tissues at different temperatures was measured to obtain the half lethal temperature(LT₅₀) through Logistic equation fitting, and LT₅₀ was served as a main parameter to evaluate the difference between organs.The results showed that the organs in the order of resistance to short term(1 hour) low-temperature stress were bud> leaf≥ stem> root, and long term(24-72 hours) low-temperature treatment would injure root first, stem the next, and then bud and leaf.In the case of short term(15 minutes) high temperature stress, the organs in the order of their resistance to temperature stress were budleafrootstem.Therefore, in practice, the relevant measures should be taken to adjust the ambient temperature before the more susceptible organ of tobacco seedling was lethally injured.