Abstract: C/SiC composites and Nb were brazed with equiatomic ratio Ti-Ni composite foils in vacuum,and the effects of surface state of C/SiC composites on the microstructure and property of the brazing joints were investigated.The results showed that the(Ti,Nb) C reaction layer between C/SiC and filler metal in the brazing joint was serrate when the C/SiC surface state was cut by the electric spark linear cutting machine,but the(Ti,Nb) C layers were both flat when the surface of C/SiC were polished and sanded before brazing.The serrate reaction layer decreased the stress concentration at the C/SiC-filler metal interface and was benefit for the joint.The shear strength of brazing joints of Nb and C/SiC at spark cutting state reached 188 MPa,which is much higher than that at polishing and sanding states.The fracture of brazing joints of Nb and C/SiC at spark cutting state took place at C/SiC base material,C/SiC-filler metal interface and filler metal,but that of the other two kinds of joints mainly occurred at the C/SiC-filler metal interface.