Abstract: Reversible solid oxide cell (RSOC) is a new energy conversion device with significant applications, especially for power grid peaking shaving. However, the reversible conversion process of power generation/energy storage poses challenges for the performance and stability of air electrodes. In this work, a novel high-entropy perovskite oxide La_0.2Pr_0.2Gd_0.2Sm_0.2Sr_0.2Co_0.8Fe_0.2O_3−δ (HE-LSCF) is proposed and investigated as an air electrode in RSOC. The electrochemical behavior of HE-LSCF was studied as an air electrode in both fuel cell and electrolysis modes. The polarization impedance (R_p) of the HE-LSCF electrode is only 0.25 Ω·cm² at 800 °C in an air atmosphere. Notably, at an electrolytic voltage of 2 V and a temperature of 800 °C, the current density reaches up to 1.68 A/cm². The HE-LSCF air electrode exhibited excellent reversibility and stability, and its electrochemical performance remains stable after 100 h of reversible operation. With these advantages, HE-LSCF is shown to be an excellent air electrode for RSOC.