Abstract: The isothermal sorption and desorption behavior of various tobacco materials, including cut rags of upper, middle and lower leaves, expanded tobacco and expanded stem, was studied by dynamic moisture sorption analyzer. The results showed that: 1) The isothermal sorption and desorption curves assumed the form of adsorption curve type III and obvious time lag was found in a desorption process; 2) The isothermal sorption and desorption behavior of cut rags of upper, middle and lower leaves was basically the same; 3) The isothermal sorption and desorption behavior of cut rags of strips, expanded tobacco and expanded stem differed significantly. At the relative humidity of ≥ 60%, expanded stem absorbed more moisture, and expanded tobacco absorbed less. While at the relative humidity of ≤ 40%, expanded stem lost more moisture, but cut tobacco lost less.