In this study, the degradation and recovery mechanisms of perovskite Ba1.0Co0.7Fe0.2Nb0.1O3−δ (BCFN) membrane under a CO2-containing atmosphere were investigated. The oxygen permeability of the BCFN membrane is degraded quickly with pure CO2 gas in the sweep side and then would be partially recovered if the sweep gas changes to 5% CO2. It is found that the existence of oxygen can stabilize the cubic perovskite structure of BCFN. Isotopic exchange test confirms the fast exchange of oxygen between the lattice oxygen of BCFN bulk and the oxygen in the formed carbonate. Pores or cracks are generated during the dynamical exchange of oxygen and serve as the permeable channels of oxygen, resulting in the partial recovery of oxygen permeability under 5% CO2 concentration.