ZnO nanostructures have been synthesized on graphite substrates by thermal evaporation of ZnO powder without a metal catalyst at a temperature of 1300. The colors of the as-synthesized products gradually change from white and brown to gray as the distance from the source material increases. ZnO particles were formed at higher temperature region. ZnO particles gradually changed into ZnO nanowire as the temperature decreased. Finally, ZnO nanowires disappeared completely and only Zn particles were observed at lower temperature region.