Dehydrogenation of ethylbenzene (EB) to styrene over iron oxide-based catalyst is an important industrial catalytic process. A great deal of insight into this reaction has been accomplished by surface science studies of the model catalysts. However, molecular understanding still lacks in the removal of the resultant hydrogen from the oxide surface. Employing gas-phase atomic hydrogen, we successfully prepared hydroxyls on an alpha-Fe2O3(0001) film with biphase surface structure under ultrahigh-vacuum conditions. Upon heating, hydroxyls react to form hydrogen and water, the latter of which results in the partial reduction of Fe2O3. These results add important insight into the complete understanding of the catalytic cycle of dehydrogenation of ethylbenzene to styrene over iron oxide-based catalyst.