Ethane dehydrogenation provides an opportunity for the effective utilization of shale gas and production of ethene. Up to now, it is still a great challenge to acquire a stable ethane dehydrogenation catalyst operated under high temperature and reductive atmospheres. In this study, we prepared an Fe-based catalyst supported on MgAl 2 O 4 with atomically dispersed iron species even after 6 reaction−regeneration cycles. Sheet-like morphology and spinel structure of MgAl 2 O 4 is beneficial for the high dispersion of Fe species. The iron species undergoes reduction, sintering, and detachment during the ethane dehydrogenation reaction, as evidenced by in situ High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy and quasiin situ 57 Fe Mossbauer spectroscopy. By contrast, the introduction of CO 2 leads to a slow deactivation, where only the partial reduction of isolated Fe 3+ species to isolated Fe 2+ species was observed. And the activity could be restored by a simple O 2 treatment. The current work sheds light on the design of high-efficient dehydrogenation catalysts.