In this work, amorphous carbon nanowires(ACNWs), formed during ion irradiating m ulti-wall carbon nanotubes (MWCNTs), were annealed at a high temperature of 2400 ℃. Transmission electron microscopy observations revealed that the body of ACNW s had transformed to a tube-like structure similar to that of the original MWCNT s, but the tip structure had various forms and was quite different from the orig inal MWCNTs. Based on the results, we proposed a conceptual model of phase trans ition mechanism.