Abstract: A novel Ag Cu In Ti alloy brazing filler metal was designed and developed by adding 21. 5% In in Ag-26 Cu-5 Ti brazing filler metal to realize active joining between Al₂ O₃ ceramic and oxygen-free copper. Solid-liquid temperature and wetting and spreading properties of the brazing filler metal were analyzed,and tensile strength and airtightness of Al₂ O₃/AgCuInTi/Cu test pieces were tested. The micro-interface microstructure of test pieces was observed by metallographic microscope and scanning electron microscope to further explore active joining reaction mechanism of AgCuInTi alloy brazing filler metal. The results showed that AgCuInTi alloy brazing filler metal could realize vacuum active joining of ceramics and metals at 750℃ and form a tightly bonded reaction interface. During the brazing process,Ti element in the brazing filler metal was enriched at the interface of Al₂ O₃ ceramics to form multiple interface products,while Ag element,Cu element,In element in brazing filler metal dissolved and diffused with oxygen-free copper to form a new compound phase. Finally,metallurgical bonding of ceramic and metal was achieved.