Abstract: To study the impact of alkali metal oxides on the performance of isobutane dehydrogenation by Cr system catalyst, the Cr2O3/Al2O3 and Cr2O3/Al2O3-CaO catalysts were prepared by incipient wetness impregnation. The performance was evaluated and BET, XRD, NH3-TPD were used to characterize the catalysts. As a conclusion, the active ingredient Cr2O3 plays an important role in the catalysis process of isobutane dehydrogenation. Alkalinity or acidity of the carrier has a great influence on the selectivity of isobutane dehydrogenation. The addition of CaO can modify the surface properties crystalline structure and surface acidity of catalyst in different extent and thus improve the selectivity of the target product as well. At the content of Cr2O3 and CaO are 20% and 5%, the conversion and the selectivity are 25.31% and 91.08%, respectively.