A variety of the modified X zeolites were used to catalyse the oxidative dehydrogenation of ethylbenzene to styrene with CO₂ for the first time. The results showed that X zeolites modified by alkali metal cation exchange, such as KX and CsX, exhibited high catalytic activity and selectivity with a good stability. The reaction temperature 818 K over the modified X zeolites is much less than 923 K over the current metallic oxide catalyst. Moreover, the co-catalysis between acid sites and base sites over the modified X zeolite was indispensable in this reaction, and the basicity of the catalyst greatly determined the selectivity of styrene. The participation of CO₂ in the co-catalysis process improves the conversion of ethylbenzene and the selectivity of styrene.