Abstract: In order to further improve the mechanical properties of commercial plastics polypropylene (PP), PP composite material incorporated with the surface-modified nano-TiO₂ particles by titanium-acid ester coupling agent NDZ-201 was prepared through the blending method. The effect of the mass fraction of TiO₂ and the dosage of NDZ-201 on the toughening and strengthening of PP matrix was investigated based on the results of the differential scanning calorimeter (DSC) and the observation of the impact fractography of the material. It was shown that the flexural strength, the modulus and the impact strength of the nanocomposite were obviously improved with the increasing of nano-TiO₂ percentage (less than 5%); and the augment of the properties dropped and turned to a decreasing tendency with the further supplement of the nano-TiO₂ content. It was also found that the addition of nano-TiO₂ promoted the crystallization of PP, leading to a much more quantity of finer β grains. Moreover, the homogeneous dispersion of nano-TiO₂ particles enhanced the obstruction to the cracks’ propagating in PP. It was indicated that the dosage of titanium-acid ester coupling agent had a parabola-like relation with the mechanical properties of nano-TiO₂/PP composite at a fixed nano-TiO₂ content, while the optimal toughening and strengthening effect could be achieved at 2% of NDZ-201.