Abstract: The nonisothermal crystallization behaviors and kinetics of polypropylene (PP) matrix composites with maleic anhydridegrafted PP (PP-g-MAH) and waste printed circuit boards (PCB) nonmetallic powders was studied with the Avrami equation using differential scanning calorimetry. The modified Avrami theories from Jeziorny's and Mo Zhi-shen's equations were adopted to analyze the DSC data. The results indicated that waste PCB powders exhibited a heterogeneous nucleation effect on the crystallization of PP. With increasing the crystallization temperature of PP, the nucleation rate became faster, the grain size distribution became narrower, and the crystallization rate was also improved. However, due to increasing of viscosity of composites, the waste PCB powders also prevented the PP matrix from crystallization at a high loading due to the increase of viscosity of composites.