The reduction of ZnO in a ZnO-supported catalyst to metallic zinc, the alloying of metallic zinc with a second metal and the evaporation of zinc species in a reductive atmosphere of hydrogen was investigated in this study. The results show that the reduction temperature was the determining factor for the transformation of zinc species. The complete removal of ZnO in a ZnO-supported catalyst can be achieved at 700 °C. The effects of different metals supported on ZnO on the transformation of ZnO were also investigated. Cu, Co and Ni species can slow the ZnO loss due to the priority for the reduction of these metal oxides and the formation of metal-Zn intermetallics. Fe based catalysts noticeably accelerated the loss of ZnO, which can be ascribed to the high oxophilicity of Fe and the strong interactions between the metal and support.