The ionic conductivity of the interlayer in the intermediate temperature solid oxide electrolysis cell (IT-SOEC) affects the polarization resistance of the oxygen electrode. Improving the ionic conductivity of the interlayer can improve the performance of the oxygen electrode. In this work, the ionic conductivity of a samarium-doped ceria (SDC) interlayer is improved by doping the transition metal oxide Fe₂O₃. The experimental results show that the oxygen electrode polarization resistance of the symmetrical cell based on the SDC-Fe₂O₃ interlayer is 0.09 Ω cm⁻² at 800 °C and under the open circuit voltage, which is obviously lower than that of the symmetrical cell based on an SDC interlayer (0.22 Ω cm⁻²). Besides, the electrolysis current of the SOEC based on the SDC-Fe₂O₃ interlayer is 0.5 A cm⁻² at 800 °C and 1.5 V, which is higher than that of the SOEC based on the SDC interlayer (0.3 A cm⁻²). The above results show that improving the ionic conductivity of the SDC interlayer in the SOEC by doping Fe₂O₃ can reduce the polarization resistance of the oxygen electrode and enhance the performance of the SOEC. Thus, this work provides an effective way for improving the performance of the SDC interlayer in the IT-SOEC.