the synergistic effect of nano-CaCO3 and PET fibers may reduce the rate of phase transformation, and maintained the formation of b crystalline. The b crystal of PP has a unique bundle structure in condensed state. In the presence of the external force, a large number of crack bands occurred in b-PP crystalline phase. They can dissipate most of the external force and thus effectively improve the mechanical strength of composite materials, especially the impact toughness.