Abstract: In order to quantitatively characterize the micro-porous structure of different kind tobacco leaves, the specific surface area and porosity of flue-cured, burley and oriental tobacco leaves were measured by N2-adsorption-desorption-method followed the pretreatment of immersing in ethanol. Meantime, the surface morphology of tobacco samples was observed by a scanning electron microscope(SEM). The results showed that: all the samples possessed obvious characters of porous medium, i.e. larger specific surface area and smaller pore volume; the porosity of oriental tobacco sample was 2.60%, that of flue-cured and burley tobacco samples was 4.78% and 10.73%, respectively; with a higher proportion of pore in leaf, burley tobacco leaf was open in structure; while oriental leaf was relatively close, and flue-cured tobacco leaf was in-between. The pore distribution characters and pore volume of samples agreed with the observation by scanning electron microscope.