The impregnation of a special grade PAN precursor fibers was carried out in a 8 wt% KMnO4 aqueous solution to obtain modified PAN precursor fibers. The effects of modification on the chemical structure and the mechanical properties of precursor fibers thermally stabilized and their resulting carbon fibers were characterized by the combination use of densities, wide-angle X-ray diffraction （WAXD）, X-ray photoelectron spectroscopy （XPS）, elemental analysis （EA）, Fourier transform infrared spectroscopy （FT-IR） and scanning electron microscope （SEM）, etc. KMnO4 as a strong oxidizer can swell, oxidize and corrode the skin of a precursor fiber,and transform CN groups to CN ones, meanwhile, it can decrease the crystal size increase the orientation index and the crystallinity index, furthermore it can increase the densities of modified PAN precursors and resulting thermally stabilized fibers. As a result, the carbon fibers developed from modified PAN fibers show an improvement in tensile strength of 31.25 % and an improvement in elongation of 77.78 %, but a decrease of 16.52 % in Young’s modulus.
