Here, we report a visible promotion effect of the B₂O₃ additive on FeO_x/Si₃N₄ catalysts in the oxidative dehydrogenation of ethylbenzene. The oxygen reactivity of FeO_x was alleviated by the strong interaction between FeO_x and BO_x species, which suppresses the overoxidation of ethylbenzene and styrene to carbon oxides, thus promoting styrene selectivity.