In this paper, La0.3Sr0.7Ti0.3Fe0.7O3-δ (LSTF0.7) composite with CeO2 is successfully prepared by infiltration method as a thin porous electrode and examined in detail as a fuel electrode for efficient reversible solid oxide cells (RSOCs) at different ratios of CO/CO2 at the temperatures of 700–850 °C. XRD analysis indicates that the cubic perovskite LSTF0.7 is stable in CO or CO2 at high temperature and compatible with CeO2 and scandia-stabilized zirconia (ScSZ) electrolyte. In electrolysis mode, the current density of 3.56 A cm−2 is obtained from the I–V curve at 2.0 V in 50% CO+ 50% CO2 at the temperature of 850 °C. The polarization resistance (Rp) of the whole cell at 800 °C is 0.28 Ω cm2 when 1.4 V is applied in the same gas composition. The corresponding activation energy of the fuel electrode under open circuit is calculated to be 81.37 kJ mol−1. In fuel cell mode, the maximal power density of 437 mW cm−2 is obtained at 800 °C in 70% CO+ 30% CO2 as well. The reversible operation at 800 °C indicates that a slow degradation phenomenon in both SOFC and SOEC modes is observed, due to the particle agglomeration of the infiltrated fuel electrode.