Solid oxide electrolysis cells (SOECs) are a new type of high-efficiency energy conversion device that can electrolyze CO₂ efficiently and convert electricity into chemical energy. However, the lack of efficient and stable cathodes hinders the practical application of CO₂ electrolysis in SOECs. Herein, a novel perovskite oxide La_0.5Sr_0.5Fe_0.95Mo_0.05O_3−δ (LSFMo) is synthesized and used as a cathode for SOECs. The introduction of Mo significantly improves the CO₂ tolerance of the material in a reducing atmosphere and solves the problem of SrCO₃ generation in the La_0.5Sr_0.5FeO_3−δ material. Mo ion doping promotes the conductivity in a reducing atmosphere and increases the oxygen deficiencies of the material, which lowers the ohmic resistance (R_s) of the material and significantly improves the CO₂ adsorption and dissociation in the middle-frequency of polarization resistance (R_p). For example, R_p decreases from 0.49 to 0.24 Ω cm² at 800 °C under 1.2 V. Further, the reduction of R_s and R_p increases the performance improvement, and the current density is increased from 1.56 to 2.13 A cm⁻² at 800 °C under 2 V. Furthermore, LSFMo shows reasonable short-term stability during the 60 h stability test.