In this study, a SrCo0.4Fe0.5Zr0.1O3-delta (SCFZ) dense mixed-conducting membrane was applied to a membrane reactor for the thermal decomposition of carbon dioxide (TDCD) (CO2 <-> CO + (1)/O-2(2)). The SCFZ membrane broke after the membrane reactor ran for about 36 h, because the eroding gases, such as CO2 and CO, corroded the membrane material. To improve the stability of the membrane reactor, the surface modification of the SCFZ membrane was applied by coating a porous layer. After surface modification on the membrane surface, the porous layer can reduce effectively the corrosion of gases for the membrane material. The effect of coating a porous layer on the membrane surface exposed to the feed side (CO2) on improving the performance of the membrane was more remarkable than that on the membrane surface exposed to the permeate side. This phenomenon can be elucidated by the reaction pathway of TDCD in the membrane reactor.