Self-lubricating fabric composites significantly enhance the tribological performance of joint bearings by minimizing friction and wear on both the inner and outer rings, thereby substantially extending their operating life. These characteristics make them excellent candidates for bearing liner materials. However, conventional polytetrafluoroethylene (PTFE)/Nomex phenolic-based fabric composites exhibit limitations in high-temperature environments, necessitating the development of more thermally stable alternatives. To address this challenge, this study introduced a novel poly-p-phenylene benzobisoxazole (PBO)/PTFE–polyimide (PI)-based self-lubricating fabric composite and proposed a PBO/PTFE–PI@M50 tribo-pair system suitable for high-temperature working conditions, utilizing M50 bearing steel as the counterpart material. Compared with Nomex fiber-reinforced self-lubricating fabric composites, PBO/PTFE–40PI (fabric composites with a resin mass fraction of 40%) demonstrated significantly superior high strength and high-temperature tribological performance. Notably, even at 300 °C, it maintained an elastic modulus of approximately 15 GPa and a tensile strength of approximately 335 MPa while achieving a low friction coefficient of 0.023 and an impressively low wear rate of 0.83×10⁻⁶ mm³/(N·m). The superior properties of the PBO/PTFE–PI@M50 tribo-pair system stemmed from the exceptional heat resistance and mechanical stability of the composite at high temperatures. Under the combined effects of “thermal–mechanical–chemical” interactions, the fiber-reinforced composite material formed a dense, uniform, and strongly stable transfer film on the surface of the M50 steel ring. Detailed analysis revealed that the stability of the film was due primarily to the viscoelastic transition of PI and PTFE at high temperatures, coupled with their strong tribo-chemical reactions with the steel ring. Given its outstanding performance, the PBO/PTFE–PI@M50 tribo-pair system holds considerable promise for advanced engineering applications.