Introducing nanoscale reinforcements into the interface between carbon fiber (CF) and resin is an effective approach to improve the interfacial adhesion of CF composites. In this paper, a facile one-pot polymerization process provides a rapid and efficient method for preparing polyphosphazene microspheres/CF hybrid reinforcement using hexachlorocyclotriphosphazene (HCCP) and bis(4-hydroxyphenyl) sulfone (BPS) as monomers. By the in situ polymerization modification, HCCP and BPS were successfully cross-linked and deposited on the CF surface. Scanning electron microscope and atomic force microscopy images show that poly(cyclotriphosphazene-co-4,4'-sulfonyldiphonel) microspheres were introduced onto the CF surfaces and the surface roughness of fibers is enhanced obviously. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm that the polymerization between HCCP and BPS has been successfully carried out. The surface modification can significantly increase the fiber roughness, polarity, wettability and surface energy, thus improving the interfacial shear strength of CF/epoxy composites, Meanwhile, the single fiber tensile strength of CF also shows an increase after modification. (C) 2017 Elsevier B.V. All rights reserved.