Lignin is a renewable material and it is abundantly available as low priced industrial residue. Lignin-based carbon fibers are economically attractive and sustainable. In addition, remarkably oxidized molecule of the lignin decreases the required time and temperature of the thermostabilization process compared to other carbon fiber precursors such as polyacrylonitrile (PAN); and thus, decreases the processing cost of carbon fiber production. The fraction 4 of softwood Kraft lignin (SKL-F4) was previously shown to be spinnable via electrospinning to produce carbon nanofibers. In this paper, we characterized different Kraft lignin powders through X-ray diffraction (XRD) analysis to measure the mean size of the ordered domains in different fractionations of softwood and hardwood samples. According to our results, SKL-F4 has largest ordered domains among SKLs and highest hydroxyl content according to Fourier transform infrared (FTIR) analysis. In addition, variations in the XRD patterns during carbon nanofiber formation were studied and the peak for (101) plane in graphite was observed in the carbon nanofiber carbonized at 1000 °C.