Nb_0.74CoCrFeNi₂ high-entropy powder brazing was used to braze C/C composites and GH4169. The effects of brazing temperature and holding time on the microstructure and shear strength of the joints were investigated to reveal the formation mechanism of the joints. Results show that the typical structure of joint is Cr₂₃C₆+(Cr,Ni)₂₃C₆/(Cr,Ni)₃C₂+NbC/fcc+Ni(s,s)+NbNi₃. With the reaction progressing on the side interface of the composite, the Cr element is gradually consumed, forming a unique gradient interfacial structure, which is conducive to relieve the residual stresses of the joint. With the increase in brazing temperature or the prolongation of holding time, the internal defects of the joints gradually disappear, but the thickness of the brittle interfacial reaction layer increases sharply, and thus the joint shear strength shows a tendency of first increasing and then decreasing. When the brazing temperature is 1260 ℃ and the holding time is 25 min, the shear strength of the brazed joint is up to 139.6 MPa, and the shear strength at high temperature of 1000 ℃ is still as high as 89.7 MPa. The high shear strength originates from the diffusion and infiltration of filler into the composite material side, which forms a strong interfacial reaction bond.