Graphene nanoribbons (GNRs) have been synthesized by unzipping oxidized multiwalled carbon nanotubes.The thickness of the GNRs synthesized is ranged from mono-layer to four layers.The morphology of prepared GNRs is strongly dependent on structure and defects of the MWCNTs.The synchrotron radiation X-ray diffractions show the d(002) spacing of the GNRs decreases with the increase of the annealing temperature.This may be caused by the removing of water molecules and oxygen-containing functional groups in the GNRs.