Abstract: Mesophase pitches were synthesized by the co-carbonization of an aromatic-rich heavy oil（FCCDO）and polyethylene glycol（PEG） under certain conditions, and the carbon fibers with excellent mechanical properties were prepared. The effects of PEG addition on the structure and properties of mesophase pitch and carbon fiber were analyzed by means of elemental analysis, X-ray diffraction and hydrogen NMR analysis et al., and the reaction mechanism of co-carbonization was speculated. The results show that with the increase of PEG addition, the softening point of mesophase pitch is gradually decreased, while the pitch yield and the number of aliphatic groups in the pitch molecular are gradually increased. At the same time, the optical structure of pitch was changed from the wide flow domain bulk mesophase to coarse flow domain mesophase, and finally to the mixed pitch with the coexistence of two phases（isotropic and mesophase components）. The mechanical properties of carbon fiber were increased at first and then decreased with the increase of PEG content. Carbon fibers with diameter of 11.4 μm and tensile strength up to 2.4 GPa were prepared by adding 5% PEG.

Key words: co-carbonization, mesophase pitch, carbon fiber, polyethylene glycol, aromatic-rich heavy oil