High-density cobalt suicide nanowires (Co-Si NWs) were synthesized by a spontaneous chemical vapor transport (CVT) method combined with microplasma treatment on a silicon wafer covered with silicon nanowires (SiNWs). The nature of the Co-Si NWs formed on the SiNWs was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD). A layer of cobalt suicide, mainly as CoSi2, was found to form on the surface of the SiNWs.