With the development of SOFC technology, stability has been more and more concerned because of its necessity in SOFC commercialization. In cathode side, contaminations such as CO₂ and H₂O existing in air are likely to influence the stability of SOFC in long-term operation. In this work, the effect of CO₂ and H₂O corrosion on high performance Ba_0.9Co_0.7Fe_0.2Nb_0.1O_3-δ (BCFN) cathode are studied through XRD measurements, conductivity and electrochemical impedance spectroscopy (EIS) analysis. The XRD results show that even in the atmospheres of 3%CO₂-3%H₂O-96%Air, the chemical reaction is happened and BaCO₃ is generated. And the conductivity of BCFN reduces obviously in the presence of CO₂ and H₂O. Compare with the single factor of CO₂ or H₂O, the polarization resistance of BCFN electrode increase obviously on the co-corrosion of CO₂ and H₂O, which declares that the co-effect of H₂O and CO₂ plays an importance role in the corrosion process on BCFN cathode.