The development of high active and stable cathode materials is one of the main challenges of intermediate temperature solid oxide fuel cells (SOFCs). Herein, a high-entropy Fe-based perovskite oxide La0.7Sr0.3Fe0.3Ni0.3Co0.3Mo0.1O3-δ (LSFNCM) is synthesized by self-propagation combustion based on La0.7Sr0.3FeO3-δ (LSF) and the electrochemical properties are systematically tested. The symmetric half-cell with the LSFNCM cathode has a high catalytic activity with a polarization impedance of 0.12 Ω·cm2 at 800 °C, and also shows outstanding CO2 resistance and chromium resistance owing to the entropy stabilization strategy. After 50h of treatment in a 10% CO2 environment, the polarization impedance of the LSF electrode increases by 8.89 Ω·cm2, while that of the LSFNCM electrode only increases by 1.81 Ω·cm2. Additionally, after being treated for 24h in a chromium vapor environment, the polarization impedance of the LSF electrode increases by 5.95 Ω·cm2, whereas that of the LSFNCM electrode only increases by 0.44 Ω·cm2. Moreover, the single cell with LSFNCM cathode exhibits the maximum power density of 932.82 mW/cm2 and the polarization impedance of 0.34 Ω·cm2 at 800 °C with humidify hydrogen as fuel. Our results indicate that high-entropy perovskite oxide LSFNCM is an active and Cr-tolerant promising cathode for SOFCs.