Abstract: Diffusion bonding between Tungsten and Steel using Co powder/Ni foil composite interlayer was carried out under the condition of 10 MPa in vacuum at 800 ℃, 900 ℃ and 1 000 ℃ for 120 minutes. The microstructure, composition, fracture characteristic and shear strength of the joints were studied. The results showed that less intermetallic compound is formed in tungsten matrix/interlayer interface of the joints bonding at 800 ℃ and 900 ℃, the shear strength of the corresponding joints is 186 MPa and 172 MPa, respectively. The shear fracture of the joints ,which is typical cleavage fracture morphology, are located in tungsten matrix near interface.When the bonding temperature is up to 1 000 ℃, a continuous intermetallic compound layer less than 2 μm is formed in the tungsten/interlayer interface, the shear strength of the joints reduced significantly to 115 MPa. The shear fracture of the joints bonding at 1 000 ℃ is also located in tungsten matrix near interface. Most of which exhibits intergranular fracture morphology.