Isotactic polypropylene (iPP) samples were prepared by sequential co-injection molding (SCIM) and conventional injection molding (CIM). The morphological structures and mechanical properties of the samples were investigated by polarized light microscopy (PLM), two-dimensional wide-angle X-ray diffraction (2D-WAXD) and tensile mechanics test. Results show that cylindritic structures of crystalline morphology are formed in overlap region of skin and core material for strong shear between skin melt and core melt during second injection. As the delay time increases, more cylindritic structures are formed. Due to the higher molecular orientation which is caused by twice shear in skin melt and stronger shear stress in core melt, the elastic modulus and tensile strength of the SCIM samples are improved compared with those of CIM samples. However, SCIM samples are broken easily because of cracks initiated in the interface of different crystal layers of SCIM samples in tensile test, which is verified by the elongation at break of SCIM samples being lower than that of CIM sample. The impact test shows that shear induced β-form iPP can improve the impact strength of samples.