Abstract: A novel Ag-(15~26)Cu-(13~20)In-(3.1~6.9)Ti active filler alloy was designed for joining of SiO_2f/SiO₂ composite to Nb at 780℃ for 20 min, 780℃ for 40 min and 800℃ for 10 min, respectively. The joints brazed with the filler alloy at 800℃ for 10 min presented the maximum average shear strength of 21.6 MPa. During the brazing process, the active element Ti diffused significantly from the Ag-Cu-In-Ti alloy to the surface of the SiO_2f/SiO₂ composite and a thin reaction layer with a thickness of 2 μm was formed close to the composite. Sound interface was also obtained between the filler alloy and Nb. The interface structure of the joint brazed with Ag-(15~26)Cu-(13~20)In-(3.1~6.9)Ti alloy can be described as the following sequence:SiO_2f/SiO₂→TiO+TiSi₂→TiO+Cu₃Ti→Ag(s, s)+Ag₃In+Cu(s,s)→Nb.