The effect of plasma and chemical methods on the stabilization of Polyacrylonitrile (PAN) nanofiber prepared by electrospinning technique, has been investigated at various oxygen contents (10%, 20%, and 30%) and KMnO4 solutions (3% and 5%). Fourier transform infrared (FT-IR) analysis of plasma and chemical oxidized samples indicated that the treated nanofibers were oxidized under different contents of oxygen plasma and KMnO4 contents by increasing the peak intensities of CO stretching band and OH- stretching vibration mode, respectively. Additionally conversion of C equivalent to N bands into CN ones in the copolymer chain was observed in both plasma and chemical methods, but changes in chemical stabilized samples were not very sensible. Field emission scanning electron microscopy (FE-SEM) images revealed that the surfaces of the plasma treated nanofibers were extremely etched. Furthermore a higher reduction in the average oxidized nanofiber diameters was observed using plasma method.