Abstract: PBO fiber has attracted wide attention for its excellent properties,but is difficult to combined with resin matrix for its smooth and chemical stable suface and the performance of the PBO fiber composites is serionsly affected.This paper describes the structure and the preparation of poly p-phenylene benzobisoxazole(PBO) fiber as well as fiber surface modification methods,including copolymerization,nanoparticle treatment,chemical and physical treatment.