The oscillation effects on the crystallization behavior of the iPP were studied by shear stage, wide-angle X-ray diffraction and DSC. The effects of strain and frequency on the crystallization behavior and morphology of iPP were also investigated. The beta form crystals were found after oscillatory shearing at the fixed frequency (2 Hz), and the beta crystallinity increased with the strains. At the fixed strain (100%), the beta crystallinity changed little with the increased frequencies. The orientation degree of the molecule chains increased with the strains. If the strain is high enough, the fiber crystals emerge. It is difficult to find the effect of frequency on the crystallization morphology of iPP. The orientation degree of the molecule chains changed little with different oscillatory frequencies. (c) 2005 Elsevier Ltd. All rights reserved.