Impact-resistance polypropylene copolymer (IPC) has been known as multiphase material in which ethylene-propylene rubber (EPR) is dispersed in homo-PP matrix (hPP). Although, the IPC has been commercially produced for several decades, the knowledge of its microstructural change under tensile stretch has not been well established. The present work, for the first time, shows the crystallite evolution of the IPC with preferentially oriented crystal lamellae in both perpendicular and parallel to stretching direction (SD). The IPC with lamella oriented perpendicular to SD exhibits higher strength and strain at break than the others. Small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques reveal that the elongation of the lamellar fibril is the main mechanism for the lamella oriented perpendicular to SD while the fibril fracture is for the lamella oriented parallel to SD. (C) 2013 Elsevier Ltd. All rights reserved.