Since being discovered, graphene shows promise as reinforcements in high-performance nano-composites. In the present study, we describe a novel strategy to design and prepare poly(p-phenylene benzobisoxazole) (PBO)/graphene composite. Graphene oxide (GO) was first modified by 4, 6-diaminoresorcinol (DAR) to improve the reactivity, solubility, and dispersivity of GO in polymer matrix. Without separation and purification, GO-DAR was further incorporated with PBO through in situ polymerization, and PBO/GO composite films were obtained by thermoforming process. The structure and morphology of GO-DAR and PBO/GO films were characterized and the mechanical and thermal properties were investigated. The incorporation of GO improved the thermal stability of PBO. Mechanical property measurements revealed that the PBO/GO films exhibited a tensile strength (148 MPa) and Young's modulus (6.2 GPa) at a GO loading of 1.5 wt%, corresponding to 39.6% and 72.2% increase compared to the PBO film, respectively. The one-pot in situ procedure wraps GO with PBO chains, improves the dispersion and alignment of GO in PBO matrix, enhances PBO chain packing order, which are considered to be the main reasons for the performance improvement of PBO. (C) 2015 Elsevier Ltd. All rights reserved.