The progress of applying HSAB theory to leather chemistry was reviewed.The stability and the tanning property of hydroxo complexes and the dechroming from leather shavings were expounded according to the absolute hardness from density-fu nctional theory and the softness from the theory of the mutual perturbation of the frontier- controfled molecular orbitals,The concept of accumulative propery of hydroxo compounds was posed as well. Finally,the future in this field was looked into.