The symmetric cell of LaNi_0.6Fe_0.4O_3-δ/Sc_0.1Zr_0.9O_1.95/LaNi_0.6Fe_0.4O _3-δ was fabricated with screen printing method. A LaNi_0.6Fe_0.4O_3-δ (LNF) cathode was modified by coating with nano-sized gadolinium-doped ceria (GDC, Gd_0.2Ce_0.8O₂) prepared using a simple combustion process within the pores of the cathode. According to the electrochemical impedance spectra (EIS), the polarization resistance of the pure LNF was 0.70 W·cm² at 750 ºC, while 0.13 W·cm² for the 21.3% GDC (by mass)-coated LNF cathode at the same temperature, which was only 1/5 of that of the pure LNF cathode. The activation energy of the 21.3% GDC (by mass)-coated LNF cathode (136.80 kJ·mol^-1) is the smallest among those of GDC-coated LNF cathodes with different contents of GDC. The 21.3% GDC (by mass)-coated LNF cathode showed the optimum performance. The results indicated that GDC coatings significantly affected electrocatalytic activity of the LNF cathodes towards O2 reduction reaction. The improved performance of GDC-coated LNF cathode was attributed to the extended triple-phase boundary (TPB) and enhanced ion conductivity of oxide.