To prepare polymer nanocomposites with enhanced performance, well dispersion of nanoparticles in matrices is necessary. In this work a new route that combines graft pre-treatment and drawing technique with melt mixing was applied. That is, nano-SiO2 particles were firstly modified by graft polymerization and then the grafted nanoparticles were melt-compounded with polypropylene (PP) producing composites filaments via drawing. Finally, the filaments were injection molded into bulk materials. The resultant PP based nanocomposites are much tougher than the unfilled polymer as characterized by either static or dynamic test, besides showing a simultaneous increase in strength and stiffness. Morphology studies indicated that drawing induced extension and separation of the grafted nano-silica agglomerates in PP matrix during making the filaments are frozen to a certain extent after nanocomposites manufacturing. In this way, the nanoparticles are well distributed in the matrix and correlated with each other throughout the entire composites, which might ensure an overall improvement of mechanical properties. Besides, β-crystal of PP developed in the drawing process can be retained in the nanocomposites, which also contributes to the toughening of PP. In view of these, the proposed drawing aided dispersion of nanoparticles might also be applicable to the preparation of other nanoparticles/polymer composites.