In this paper, coiled carbon nanofiber and straight carbon fibers were easily obtained by chemical vapour deposition (CVD) using copper nanoparticles as a catalyst. Effect of the size of metal copper nanoparticles on the morphology of carbon fibers was investigated, and we proposed that the nanoparticles with bigger diameter are apt to synthesized straight carbon fiber, and the smaller nanoparticles to coiled carbon nanofibers. The product in the experiment was characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD).