Decomposition of sodium chlorate catalyzed by iron oxide in the presence of barium peroxide and hydroxide is studied by thermogravimetric analysis. Barium peroxide and hydroxide are moderately active catalysts by themselves but are inhibitors when used together with iron oxide. A loading of 1% barium peroxide or hydroxide can significantly reduce the activity of the iron oxide and raise the decomposition temperature of sodium chlorate. The inhibiting effect decreases with increased loading of the barium compounds due to the formation of barium ferrate. catalytic activity change of the iron oxide in the presence of barium peroxide and hydroxide is discussed based on the electron configuration change of the iron ions.