The effect of the physicochemical characteristics on the moisture diffusion of tobacco was studied.In this research, the physical structure (specific surface area and pore volume) and major chemical components (total nitrogen, protein, pectin, starch, water-soluble sugar, and total sugar) of tobacco were determined. The effective diffusion coefficient of tobacco ranged from 0.5×10 −14 to Downloaded by [University of California Davis] at 15:25 27 December 2014 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 6.5×10 −14 m 2 s -1 depending on environment humidity (RH = 33%, 43%, 75%, 83%) at 30 °C. This coefficient was significantly affected by the pectin, total sugar, and water-soluble sugar content and specific pore volume of tobacco during desorption.