It is already reported by our group that zirconia has good catalytic activity in the dehydrogenation of ehtylbenzene with carbon dioxide as oxidant. Tetragonal and monoclinic zirconia are prepared by precipitation method. Tetragonal zirconia showed better ethylbenzene convbersion and styrene selectivity than monoclinic zirconia. This can be ascxribed by the difference of the amount of defdcts on zirconia surface and the difference of the surface badicity. Therefore, tetragonal zirconia is more efficient in this catalysis and there is more possibility of improvement in the modification of tetragonal zirconia