A novel Ni-based high-temperature brazing filler was developed by adding 5% atomic percent of Si to the ternary eutectic composition of Ni79Nb10B11. This new filler was used to successfully braze C_f/SiC composites to 304 stainless steel at 1 100 °C for 30 minutes. The wettability of the Ni-Nb-B-Si filler on C_f/SiC composites was evaluated using the sessile drop method， and its melting point was determined by DTA. The microstructure of the brazed joints was analyzed by SEM and EDS， while the mechanical properties were assessed through shear tests. The results show that the Ni-Nb-B-Si filler consists mainly of NbNi₈ and Ni-B-Si compounds， with an actual melting temperature range of 1 036~1 060 ℃， which is higher than that of traditional Ag-Cu-Ti and Ti-Zr-Cu-Ni fillers. The filler exhibited good wettability on C_f/SiC composites， with a contact angle of 17.5°. During the brazing process， B and Si atoms diffuse into the 304 stainless steel substrate， and Ni react with SiC to form Ni₂Si and C. The joining layer is primarily composed of Nb₆Ni₁₆Si₇， a Ni-based solid solution， and Cr compounds. The shear strengths of the joint at room temperature and at 900 °C are 32.0 and 21.2 MPa， respectively， with fracture occurring at the interface between the C_f/SiC composite and the joining layer. These results indicate that the novel Ni-Nb-B-Si filler has promising application prospects for joining high-temperature ceramic matrix composites to stainless steel.