The addition of BaCl2 to Ho2O3 could improve considerably both the C2H6 conversion and C2H4 selectivity in the oxidative dehydrogenation of ethane (ODE) reaction. At 640 degrees C, C2H6:O-2:N-2=2:1:4, and W/F=0.6 g s ml(-1), C2H6 conversion of ca. 57 % , C2H4 selectivity of ca. 68 %, and C2H4 yield of ca. 39 % were observed over the 50 mol% BaCl2/Ho2O3 catalyst within a reaction period of 40 h. We conclude that the addition of BaCl2 to Ho2O3 Can 1. enhance oxygen activation, 2. prevent a certain amount of active basic sites from being occupied by CO2, and 3. suppress C2H4 deep oxidation. The presence of Cl-ions could induce the formation of new active sites suitable for C2H4 generation. For the 50 mol% BaCl2/Ho2O3 catalyst, chlorine leaching was insignificant during the ODE reactions. This could be the reason why the catalyst was stable within the reaction period of 40 h.