In this study, we introduce a novel flash light sintering (FLS) method to address the issue of secondary phase formation in conventional high-temperature thermal sintering processes. The microstructure and cross section of the Lanthanum strontium cobalt (LSC) air electrode were analyzed using field emission scanning electron microscopy (FE-SEM). The presence of secondary phases was evaluated using X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) in SEM. Electrochemical performance was assessed using NiO-YSZ anode-supported LSC cathode cells at 750oC. The maximum power density of the thermally sintered LSC cathode at 900oC was 272.4 mW/cm², while the flash light sintered LSC cathode by 18.5 J/cm² achieved 2,222 mW/cm². These results demonstrate that the flash light sintering process can effectively prevent secondary phase formation and successfully sinter the electrode, thereby enhancing the performance and reliability of SOFCs.