Enhanced activity of Ni wire in CO hydrogenation has been observed when the metal surface is incompletely reduced. The catalytic behavior has been studied in a flow reactor for different H₂/CO ratios, and the carbon species accumulated on the metal surface during reaction have been analyzed by Temperature-Programmed-Surface-Reaction（TPSR）. It has been concluded that the surface or sub-surface oxygen remaining on the catalyst due to incomplete reduction plays an important role in determining the metal catalyst behavior. The extent of metal reduction in addition to the metal surfac area has to be considered in estimation of the intrinsic activity of Ni catalysts.