The Gadolinium Doped Ceria (GDC) diffusion barrier layer was formed on the Yttrium Stabilized Zirconia (YSZ) electrolyte to apply La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) cathode system for lowering the operating temperature of Solid Oxide Fuel Cell. In this study, YSZ and GDC layers were coated by one-side dip coating method which possibly coat one-side of anode substrate. Cu(NO₃)₂ was infiltrated into pre-sintered substrate of anode and electrolyte as a sintering aid for lowering the co-firing temperature which was enough to produce dense electrolyte layer. LSCF-GDC cathode was coated on the GDC layer by screen printing method. The cells were operated at 600℃ and 650℃. The microstructures of the surface and cross-section were observed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The ohmic and polarization resistance were measured by the Electrochemical Impedance Spectroscopy (EIS).