Abstract: In this study, the Ag-CuO-Al₂O₃ composite braze was successfully developed through adding Al₂O₃ nanoparticle reinforcements, which was suitable for reactive air brazing (RAB) solid oxide fuel cell (SOFC) components. The RAB joining process was investigated in detail. The cell was successfully joined to the aluminized steel at 1 050 ℃ for 30 min. The interfacial joining properties were studied. The evolution behavior of Al₂O₃ nanoparticle reinforcements in the RAB process was also analyzed. As-brazed joints were tested in high-temperature service atmospheres. The microstructure properties of joints after aging in high-temperature oxidization (air) and reduction (H₂-50H₂O-N₂) atmospheres was investigated. It is shown that the Al₂O₃ protective layer of aluminized steel had good protective effects on the steel matrix, avoiding its performance degradation during brazing and high-temperature aging. The Al₂O₃ protective layer play a key role in ensuring the stability of joint structure. The influence of the high-temperature service on the gas-tightness of joints was systematically studied. The applicability of the Ag-CuO-Al₂O₃ composite braze used for RAB joining SOFC components was comprehensively evaluated.