The surface properties of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) perovskite electrode are modified with HNO3 treatment to improve its catalytic activity towards oxygen reduction reaction between 500–650 °C. The surface concentrations of A-site cations are reduced after the acid etching. After the calcination at 1150 °C, severe segregation of Sr is observed on the surface of untreated LSCF powder, which is suppressed remarkably with the HNO3 pretreatment. Highly reactive oxygen species and Fe4+ species are formed on the surface of LSCF after the HNO3 treatment, which are beneficial to oxygen reduction reaction. The reduction of oxygen species adsorbed on the LSCF surface, the rate-determining step of the electrode process, is accelerated significantly with the acid etching.