Reduction characteristics of Co or Mo oxide catalysts supported on activated carbon and alumina was studied under hydrogen atmosphere using a flow microbalance reactor. The results of TPR study and reduction kinetics study analyzed by the Elovich mechanism showed that the catalysts supported on the carbon had higher rate of reduction and lower variation of reduction activation energy with the extent of reduction. This suggested that the carbon support had less and more homogeneous interaction with the metal phases. The precursor oxide states examined by XRD and DRS and the reduced states investigated by ethylene hydrogenation and hydrogen chemisorption were in good correlation with the proposed explanation.