Abstract: The deformation and force-bearing processes of leather in drum during tanning were investigated under different rotating speeds. The complicated deformation process of leather in drum was first simplified to a periodic process from a circle to an oval, and the calculation model of deformation was established. Then the deformation and force-bearing processes of leather in the drum were quantitatively validated through visualization experimental data. It was proven that this model was scientifically sound. Moreover, using high speed (such as 15 r/min in this experiment) at the beginning of tanning and low speed (such as 5 r/min in this experiment) at the end of tanning can result in large deformation and pushing force of leather, thereby benefiting the mass transfer of leather chemicals and enhancing tanning performance. The obtained results are expected to improve the energy conservation of leather industry.