Abstract: The paraffin embedded mature, ripe, and overripe fresh leaves from upper, middle and lower stalk positions of flue-cured tobacco cv.K326 were sliced rapidly, and the tissue of lamina was observed.The results showed that the width of epidermis cell and the thickness of spongy tissue were increased, and the thickness ratio of palisade to spongy decreased with the increase of maturity degree.The palisade and spongy tissues of ripe leaves had the la rgest cell clearances.The thickness of palisade and spongy tissues was significantly correlated with leaf thickness, and the correlation coefficients were 0.79 and 0.94, respectively.