Tensile strength and morphology of blends of high-density polyethylene (HDPE) and polypropylene (PP) obtained by oscillating packing injection molding were investigated via Universal Testing Machine, DSC, and SAXS. Tensile strength is greatly enhanced from 24.5 MPa to more than 90 MPa for pure HDPE and for blends with PP content less than 10 wt %. There exists a sharp decrease of tensile strength when PP content is more than 10 wt %. The shear-induced morphologies with core in the center, oriented zone surrounding the core and skin layer are observed in the cross-section areas of the samples. Interestingly, a sharp decrease of oriented zone is seen when PP content is more than 10 wt %, associated with the sharp decrease of tensile strength. DSC result shows double melting peaks with a high-temperature melting peak that is not present in the endotherm obtained from the central core and Obtained from the samples by static packing injection molding, which indicates the existence of shish-kebab structure in the oriented zone, However, there is no difference of crystallinity between the samples by oscillating and by static packing injection molding. SAXS was used to analyze the complicated morphologies induced by shear stress, and results show that the Crystal thickness could be greatly increased under shear stress.