The wetting behaviors of the Co50NiCrWB filler metal on the DD5 single crystal and GH3039 superalloy was investigated at 1160 ℃ for 15 min, and DD5 and GH3039 joints are obtained by brazing. The microstructure and mechanical properties of the joints are analyzed. The result indicates that Co50NiCrWB filler metal has good wetting properties on the surface of DD5 single crystal and GH3039 superalloy. The joint is consisted of reaction zone and diffusion-affected zone. The main phases of the reaction zone are Ni–Co–based solid solution dissolved with Cr, Cr–rich boride phase and (Co, Cr, W, Re)–rich boride phase. The average tensile strengths of the brazed joints at 900 ℃ reached 193 MPa, and the lasting life of the joints at 900 ℃ /40 MPa is up to 221 h. The fracture observation of the tensile specimen shows that the fracture occurs in the brazing filler metal reaction zone, which is characterized by brittle fracture.