Poly(p-phenylene benzobisoxazole) (PBO) fibers, due to their high strength, high modulus and excellent mechanical properties, have become one of the most promising reinforcing materials for resin matrix composites; however, their dense and smooth surfaces and high inertness of the chemical structure lead to poor interfacial strength between the fibers and the matrix, which seriously restricts the performance of the composites. Therefore, it is important to regulate the interfacial properties between PBO fibers and resin matrix. This paper expounds how the physical and chemical changes on the fiber surface contribute to the adhesion strengthening mechanism at the interface. The research progress of interfacial modification techniques for PBO fiber composites in recent years is systematically introduced. Moreover, typical composite interfacial models and their mechanisms are introduced to provide theoretical basis and new ideas for the evaluation and modification methods of the interfacial properties of composites.