Abstract: This paper conducted solid-state diffusion bonding on superalloy GH4099, in which Nickel foil, in thickness of 2, 4 and 10 μm, was inserted as interlayer. The welding process was implemented in vacuum at solution temperature 1 120 ℃ under 4 MPa of axial compressive stress for 60 min of dwelling time. The microstructure and element migration and tensile property of the joint were measured by using SEM, EDS and tensile test. The results showed that, the adding of Nickel interlayer accelerated elimination of joint porosity. When Nickel interlayer thickness decreased from 10 μm to 2 μm, the grain symbiosis and chemical homogeneity were improved; whereas, the strengthening phases were precipitated more adequately from the joint, which contributed to the rise of tensile strength and the average strength of 1 180 MPa. However, the decrease of interlayer thickness made the joint performance sensitive to the surface roughness, meanwhile mechanical constraint provided by the base materials inhibited the plastic flow, resulting in the decrease of joint elongation.