Sr0.9Co0.3Fe0.7O3+delta was doped by cerium via solid state reaction method to enhance its electrochemical activity when used as the cathode material for solid oxide fuel cells (SOFCs). The obtained novel cathode materials (Ce0.1Sr0.9)(x)Co0.3Fe0.7O3-delta ((CS)(x)CF) were confirmed to have a Pm-3m cubic perovskite structure when x was in the range of 0.90-1.10 based on X-ray diffraction (XRD) analysis. A-site deficiency was generated as x < 1.0 but A-site excess(x > 1.0) resulted in impurity phases. The generation of A-site deficiency was confirmed based on X-ray photoelectron (XPS) and O-2-TPD measurements. As a result, SOFCs with (CS)(0.9)CF cathode showed the maximum power density of 0.571 Wcm(-2) at 800 degrees C and the maximum conductivity of 109.6 Scm(-1) at 700 degrees C.