No catalyst-assisted zirconium carbide nanowires (ZrCNWs) were successfully synthesized by thermal evaporation and in situ reaction using carbon nanotubes (CNTs) and ZrCl4 as carbon and zirconium sources. Vapor-Solid (VS) mechanism was proposed to explain the growth process of ZrCNWs. The ZrCNWs prepared at 1400 degrees C have a single crystal structure with the diameters of 130-290 nm. The axial growth direction of ZrCNWs is [111] and the yield is 76.5 wt%. After heat treatment at 1700 degrees C, 2100 degrees C, and 2450 degrees C, the diameter of ZrCNWs increased and their aspect ratio decreased. By simulating the thermal stress of a single ZrCNW, it is speculated that the coarsening and fracture of ZrCNWs are caused by the overall slip of the atomic layers and the stress concentration at the dislocations.