A efficient and novel experimental method for synthesis and welding of amorphous carbon nanowires (ACNWs) by using double ion irradiations and heat-treatment is described. Experimental samples were characterized using high resolution transmission electron microscopy (HR-TEM). The results demonstrate that the proper combination of double ion irradiations and heat-treatment may make the multiwalled carbon nanotubes (MWCNTs) to become amorphous carbon nanowiro, thus enabling the welding of crossed ACNWs. In addition, the atomic evolution in carbon structural phase transformation is briefly discussed in connection with the current prevailing ideas.