Abstract: The dynamic changes of moisture content,total alkaloid,reducing sugar,total sugar,petroleum ether extract in cut tobacco during drying were investigated with a laboratory cylinder drier,and the effects of cylinder wall temperature(Tw) were also studied.The results showed that:1) the change of moisture content in cut tobacco during drying was in accordance with Fick's second law;the values of De(effective diffusion coefficient) of flue-cured tobacco were less than that of burley tobacco;De of all tobacco increased with the increase of Tw,however the relative variation of upper leaf was narrower than that of middle leaf;2) generally,with the prolongation of drying duration,the contents of total alkaloid and reducing sugar decreased linearly,and decreased rapidly as Tw increased;3) though the change of total sugar content was not regular,it decreased sharply at the end of a drying process at Tw 160℃;4) petroleum ether extract content varied in a similar way under different experimental conditions,it increased first and then decreased,and peaked at the moisture content range of 8% to 12.5%.