Rare earth solution (RES) and coupling agent surface modification were employed towards poly-p-phenylene benzobisthiasole (PBO) fibers, and impact and tribological properties of the untreated and treated PBO/TPI composites were evaluated. The results show that both RES and coupling agent surface modification can improve the interfacial adhesion between PBO fibers and TPI matrix, and accordingly enhance the impact and tribological properties. Compared with the untreated and coupling agent treated PBO/TPI composites, the RES treated composite has better interfacial adhesion. The RES surface modification is the most effective one to improve the impact and tribological properties under the same test conditions. This is because that the ratio of oxygen/carbon on the surface of RES treated PBO fiber is the maximal one, which indicates the content of polar groups on the surface of PBO fibers increases compared with the others. The increase in the amount of polar groups could strengthen the interfacial adhesion between PBO fibers and TPI matrix effectively.