Abstract: In order to accurately characterize the kinetic characteristics of cut strips in the process of dehydration,the variation of pore structure in cut strips of flue-cured and burley tobaccos during rapid convective drying in a downflow bed was analyzed.The process of cut tobacco drying and shrinking was fitted by a mathematic model,and the model for moisture diffusion during drying taking into account the shrinking deformation was developed and verified.The results showed that:1) With the decrease of pore volume of cut strips of flue-cured and burley tobaccos during drying,the proportion of volume of pores of>0.5 μm in size decreased,while that of<0.05 μm increased.The fractal dimension of the two tobaccos ranged from 2.45 to 2.71 at different drying stages,which indicated that their pore structure possessed fractal characteristics.2) The linear superposition model described the shrinkage of cut strips during drying pretty well,the linear correlation coefficients for the volume ratio(V/V₀) and moisture content ratio(X/X₀) between cut strips of the two tobaccos were higher than 0.99.The shrinkage model was used to revise the moisture diffusion model based on Fick's second law,so that the fitting accuracy of experimental data increased from 0.906 9 to 0.958 0.3) From the revised moisture diffusion model,it was found that the effective diffusivity of moisture was overestimated when the shrinkage of cut strips during drying was neglected,which indicated that the shrinkage of cut strips impacted a negative influence on mass transfer process during drying.