The vacuum brazing experiment of Si₃N₄-MoSi₂ composite ceramic and Nb was successfully carried out with high-temperature active brazing filler TiZrNiCu. The typical interface structure and formation mechanism of the brazing joint were studied, and the effects of brazing temperature and holding time on interface structure and mechanical properties of brazed joints were analyzed. The results show that the typical interface structure of the joint was Nb/β-Ti/(Ti, Zr)₂(Cu, Ni)+β-Ti+(Ti, Zr)₅Si₃/TiN+(Ti, Zr)₅Si₃+MoSi₂/Si₃N₄-MoSi₂. Brazing temperature and holding time affected the amount and distribution of (Ti, Zr)₅si₃ compound in the brazing seam by controlling the diffusion degree of Si atoms in Si₃N₄-MoSi₂ composite ceramic to the brazing filler, thus affecting the shear strength of the brazed joint. The highest room temperature shear strength of Nb/Si₃N₄-MoSi₂ joint was 112 MPa at 920 ℃/10 min. The high-temperature shear strength of Nb/Si₃N₄-MoSi₂ brazed joint was 123 MPa and 131 MPa at 500 ℃ and 600 ℃, respectively.