In this paper, Sm0.5-xGdxSr0.5CoO3-δ(SGSC, x=0 and 0.2) powders were prepared using the solid-state reaction method. Their structure was identified by XRD. All powders formed the perovskite phase when calcined at 1100°C for 5 h. Sm0.3Gd0.2Sr0.5CoO3-δ/Gd0.1Ce0.9O1.95slurrieswere screen printed onto both surfaces of Gd0.1Ce0.9O1.95electrolyte and fired at different temperatures to fabricate the composite cathodes. The electrochemical property of the composite cathodes was characterized by the alternative current impedance spectroscopy. The impedance resistance of the composite cathodes increased with the increase of sintering temperature. For instance, the impedance resistance of the composite cathode fired at 1000 °C was 0.0875 Ω·cm2at 700 °C, while it was 0.175 Ω·cm2when fired at 1100 °C.