Co/Al2O3 catalysts with different Co3O4 loadings were studied in catalytic dehydrogenation of propane. The optimal results of 21.5 wt% propylene yield and 83.6 % selectivity were obtained at 5 wt% loading. XRD, DRS and XPS results showed that at loadings below 10 wt%, the "surface Co spinel" formed from tetrahedral Co2+ ions during the course of reaction constituted the active site for dehydrogenation reaction. Whereas at high loadings (above 10 wt%), only Co3O4 crystallites presented, which were easily reduced to metallic Co species, resulting in dramatically enhanced cracking reaction and the formation of abundant methane. [GRAPHICS] .