Dense and thin LaMnO3 and YSZ was deposited on porous La0.85(Sr)0.15MnO3 substrate in order to study oxygen redox behavior at an interface of LaMnO3/YSZ. YSZ film was deposited by the CVD - EVD method on porous substrate at first, LaMnO3 film was deposited on the YSZ film by the EVD method. Results of the AC impedance measurements showed that electrode interface conductivity (σe) was directly proportional to the surface area, while σe v. s. TPB (Three Phase Boundary) length plot did not show linear relationship. It was concluded that LaMnO3 surface as well as TPB region, is an active site for oxygen redox reaction when the LaMnO3 film electrode is very thin (about few μm).