This work aimed to study the effect of surface modification of potassium titanate whiskers on the mechanical properties of polypropylene composites, in order to explore the optimal surface modification method. Silane coupling agents KH550, KH570, 12 alkyl trimethyl silane modification, titanate coupling agent NDE311, were used respectively to modify potassium titanate whiskers (PTW), and the modified potassium titanate whiskers, glass fiber and pp were used to prepare polymer PP/GF/PTW composites by melt blending. The effects of PTW before and after modification by different coupling agents on the properties of polypropylene/glass fiber composites were compared, and it was found that the modified PTW could improve the mechanical performance of the composites. The effects of PTW modified by different coupling agents on the properties of polypropylene/glass fiber composites were compared, and it was found that after treatment with KH550 coupling agent, the bending performance, stretch performance and impact performance of the composites were improved by 58.63%, 16.07%, and 63.1%, respectively, as compared to those without modification. The PTW modified by KH550 coupling agent led to the composites with the best comprehensive properties.