Ag-Cu-Ti and Ag-Cu-Ti+B4C composite brazing alloys were successfully used to braze the B4C-TiB2-SiC-TiC (BTST) composite ceramic. The effects of brazing temperature and holding time on the interfacial microstructure and mechanical properties of the joints were investigated. The results show that Ag-Cu-Ti brazing alloy had a good wettability with BTST and Ti reacted with BTST to form TiC and TiB. The thickness of reaction layer increased with the increase of brazing temperature or holding time, and Ag-Cu eutectic alloy formed in the brazing seam. The bending strength of the joints increased with the brazing temperature or holding time first and then decreased. The addition of B4C into the Ag-Cu-Ti refined the microstructure of brazing seam and reduced the thickness of reaction layer. The maximum bending strength of the joint achieved was 314 MPa, when the BTST composite ceramic was brazed at 890℃ for 15 min using the Ag-Cu-Ti with 1 wt.% B4C.