Abstract: The early structural and mechanical models for keratin fibers in moisture-stre tching are still used as the wool slenderzing technology and theory,and it is cl aimed that the slenderizing stretch is resulted from the change of the transform ation from α-heli x configuration to β-fold of macromolecules.The comments on the point of view have been made, the `slippage slenderizing' machanism for wool tops ar e proposed, and the experimental validation has been carried out on the new theory.