A descaling and oxidation pretreatment was employed to maximize the yield of cortical cells in the disintegration process of wool fiber. The results indicated that the productivity of intact cortical cells was greatly increased by moderate oxidation pretreatment in 1.6 % per-acetic acid within 2 h, but the yield would be decreased by further oxidation pretreatment. In order to give a reasonable explanation for this fact, the effect of the increasing time of oxidation pretreatment on the yield of intact cortical cells was investigated by means of spectral analysis using FT-IR and XRD. The intensity of the peak at 1040 and 1173 $cm^{-1}$ in FT-Infrared spectrum gradually increased with increasing oxidation pretreatment time, suggesting that more and more SS bonds were cleaved to form cysteic acid. X-ray Diffraction investigation showed that the crystallinity of wool fiber obviously decreased when the time of oxidation pretreatment exceeded 2 h. The combined results of FT-IR and XRD revealed that SS bonds in the amorphous region of wool fiber were first cleaved in the fiber components. The selective cleavage of SS bonds in the amorphous region by the appropriate oxidation pretreatment can effectively decrease the bonding force between the components of wool fiber and enhance the yield of intact cortical cells.