Studies on the use of polyolefin elastomer (POE) and high density polyethylene (HDPE) for toughening polypropylene (PP) to meet the demands of automobile bumpers were conducted. The effect of the basic resin, POE and the influences of the POE amount and HDPE doses on the mechanical properties of the blended composites were discussed. The morphology of impact fracture sections were characterized by scanning electron microscopy (SEM) while the crystalline properties were investigated by DSC. The effect of the composites' morphology on mechanical properties was also discussed. Results showed that POE could improve the impact strength of PP while the use of HDPE had obvious effects on synergistic toughening. SEM images and DSC data analysis testified to the relationship between morphology, crystallinity and the mechanical properties.