The work aims to study the effect of titanium dioxide on the mechanical properties of polypropylene/six potassium titanate whisker composite, and work out the optimal mass fraction of TiO2. Firstly, titanium dioxide (TiO2) and potassium hexatitanate whisker (SPTW) were modified by silane coupling agent KH550. Then, PP/PP-g-MAH/ SPTW/TiO2 composite was prepared by melt blending of modified TiO2, potassium hexatitanate whisker, maleic anhydride grafted polypropylene (PP-g-MAH) and polypropylene (PP). Finally, the influences of different content of titanium dioxide on properties of polypropylene/potassium titanate whisker composite were compared. The research showed that titanium dioxide could significantly improve the mechanical properties of the composite. With the increase of the content of titanium dioxide, the mechanical properties of the composite increased at first and then decreased. The bending strength, tensile strength and impact strength of the composite increased by 35.2%, 41.2% and 33.7% respectively when the amount of titanium dioxide was 1%. Subsequently with the increase of TiO2 content, the flexural strength of the composite gradually began to decline, and the tensile strength and impact strength gradually began to decrease when the amount of the composite was added for more than 2%. In conclusion, when the TiO2 mass fraction is about 2%, the composite has the best mechanical properties.