Rare earth and coupling agent surface treatment methods were employed toward poly-p-phenylenebenzobisoxazole (PBO) fibers. X-ray photoelectron spectroscopy measurement was used to analyze the surface characteristics of untreated and treated PBO fibers. The friction and wear behavior of the thermoplastic polyimide (PI) composites filled with differently surface-treated PBO fibers, sliding against GCr15 steel under oil-lubricated condition, was investigated on a reciprocating ball-on-block UMT-2MT tribometer. Scanning electron microscope investigation of worn surface morphologies of PBO/PI composites showed that rare earth treatment was more effective than coupling agent treatment to improve the friction and wear behavior of PBO/PI composites under given load and reciprocating sliding frequency. The mechanism of the friction and wear behavior of PBO/PI composites was discussed.