The notched Izod impact properties of polypropylene (PP) filled with hollow glass beads (HGB) have been measured at room temperature to identify the effects of the particle contents, size and its distribution on them in the present paper. The mean diameters of the particles were 11, 35, and 70 mu m, and named TK10, TK35 and TK70 respectively. The surface of the particles was pretreated with silane coupling agent. The results showed that the notched Izod impact strength (sigma (I)) of the filled systems increased gently with increasing the volume fraction (phi (f)) of the fillers when phi (f) was less than 15%, and then it decreased. When phi (f) was 10%, sigma (I) decreased with an increase of the mean diameter of the particles. Furthermore, the impact fracture surface of the specimens was observed by using a scanning electron microscope (SEM). The improvement of the impact toughness of the composites might be mainly attributed to the shear yielding first of the matrix around the beads to absorb relevant deformation energy under impact load.