The effect of surface treatment of glass beads with a silane coupling agent and the filler content on the notched Izod impact properties of the filled polypropylene (PP) composites has been investigated. It was found that the impact fracture energy of the composites, E-IC, increased with increasing the volume fraction of glass beads, phi(f); the influence of surface treatment of glass beads on E-IC was insignificant; the brittle-ductile transition (BDT) phenomenon occurred when phi(f) was about 10%. A modified percolation model for BDT in thermoplastic-rigid particle blends is proposed under the basis of predecessors＇ work. The results show that the BDT of the composites in impact can be considered as a percolation process.